Open Access Repository of Indian Theses

Marrapu, Balakrushna

Synopsis 
i 
Introduction 
Phospholipids (PLs) are important constituents of most of the biological 
membranes. As the demand for bioactive molecules is increasing day by day, substantial 
interest is growing rapidly to design more and more structured phospholipid molecules 
useful for food, industrial and biological applications. The thesis entitled “Chemo-
enzymatic Synthesis of Novel Structured Phospholipids and their Biological 
Evaluation” deals with the development of novel methodologies for the partial synthesis 
of structured phospholipids, their characterization and biological evaluation. The entire 
thesis is divided into five chapters. 
 
Chapter 1: Introduction to Phospholipids 
This Chapter gives introduction about classification of phospholipids, 
nomenclature, structure and occurrence of phospholipids. Various methods used for 
qualitative and quantitative identification and analysis of phospholipids are briefly 
reviewed. The chapter also gives information on biological evaluation of various 
structured phospholipids synthesized either by partial or total synthesis. Salient features 
of various methods available in literature for the synthesis of mono acyl, diacyl and 
mixed chain phospholipids using chemical and enzymatic process are also briefly 
reviewed. 
 
Chapter 2: A Novel Methodology for the Synthesis of 1-Acyl-sn-Glycero-3-
Phosphocholine and 1,2-Diacyl-sn-Glycero-3-Phosphocholine 
In addition to their normal biological role, phospholipids are being used in several 
areas like surfactants, pharmaceuticals, paint, dye, cosmetics and food industries. In this 
chapter, a simple, efficient and environmentally benign methodology was developed for 
the synthesis of saturated and unsaturated fatty acid containing phosphatidylcholines (1-
acyl-sn-glycero-3-phosphocholine, 7 compounds and 1,2-diacyl-sn-glycero-3-
phosphocholine, 11 compounds) were developed from GPC with fatty acids/fatty acid 
chlorides employing kieselguhr as catalyst in solvent free conditions and without using 
any additional acylating catalyst (Scheme 1). The yields of short chain fatty acid based 
PCs were very low when GPC-kieselguhr complex was reacted directly with C3-C6 fatty 
Synopsis 
ii 
acids. However, the yields were improved when shorter chain (C3-C6) fatty acid chlorides 
were used in place of fatty acids. 1-Acyl PCs were selectively obtained when GPC-
kieselguhr complex was reacted with long chain (C8-C18) fatty acids. 1,2-Diacyl PCs 
were yielded when the reaction was carried out with long chain fatty acid chlorides. The 
yields of the products were in the range of 95-98% for 1-acyl PCs and 96-99% for 1,2-
diacyl PCs.  
 
       Scheme 1. Synthesis of 1-Acyl-sn-Glycero-3-Phosphocholines and 1,2-Diacyl-sn- 
Glycero-3-Phosphocholines 
 
The novelty of this methodology is employing kieselguhr as a heterogeneous 
catalyst for the first time and the kieselguhr was separated from reaction mixture and 
washed with methanol and reused for 5 times without loss of any activity. All the 
products were characterized by NMR and MS analysis and also further confirmed by 
chromatographic (HPLC and GC) techniques. This method is quite attractive for the 
preparation of symmetrical phosphocholines. As all the reaction steps are very simple, the 
method can be upscaled very easily for commercial exploitation for the preparation of 
both lyso PC and symmetrical 1,2-acyl PCs. 
 
Chapter 3: Enzymatic Synthesis of 1-Lipoyl-2-Acyl Phosphatidylcholines 
Phospholipids especially structured phospholipids are known to have applications 
in studies related to functions of biological membranes and in studies of function and 
folding of membrane-bound proteins. Literature reports are abundantly available for the 
synthesis and studies of phospholipids with a variety of fatty acids, but same is not the 
Synopsis 
iii 
case with fatty acids with different functionalities like hetero atom containing fatty acids. 
Very few reports are available on the synthesis of PLs involving active functional groups 
of fatty acids like sulphur based, amines, carboxylic acids, carbonyl compounds etc 
which suggests that there is scope for further research in this direction. Sulfur containing 
lipoic acid (LA) has been gaining importance as drug of the future due to its numerous 
biological activities. LA exhibits antioxidant activity in both oxidized and reduced forms. 
LA has potential as therapeutic agent in ischemia-reperfusion injury, heavy metal 
poisoning, radiation damage, neuro degeneration, HIV infection and the treatment of 
diseases such as atherosclerosis, thrombosis, diabetes, inflammatory. This chapter deals 
with the bioorganic synthesis of four novel phospholipids, 1-lipoyl-2-acyl 
phosphatidylcholine from 1, 2-diacylphosphatidylcholine (DPPC, DOPC, soya/egg PC) 
and lipoic acid as substrates via lipase catalyzed (Lipozyme RMIM, TL IM, Candida 
antarctica and R. oryzae lipases) transesterification reaction at controlled water activity 
(Scheme 2) and only Lipozyme RM IM exhibited the maximum incorporation of lipoic 
acid into phosphatidylcholines. The optimum conditions for the formation of desired 
products with RM IM lipase as catalyst were found to be 1:30 molar equivalents of PC to 
lipoic acid with a lipase concentration of 75 mg/mL of substrate mixture at room 
temperature with various reaction time periods (96-120 h) at aW of 0.11. A low water 
activity, high lipoic acid concentration and prolonged reaction times were necessary for 
the product formation (70-87%) and maximum conversion (80-97%) of the starting 
material.  
 
Scheme 2. Synthesis of 1-Lipoyl-2-Acyl Phosphatidylcholines 
All the products were characterized by NMR and MS analysis. All the products 
were evaluated using three in vitro methods such as 2,2-diphenyl-1-picryl-hydrazyl 
radical scavenging activity, superoxide radical scavenging activity and inhibition of lipid 
peroxidation assay compared with BHT and α-tocopherols as standard antioxidants. All 
Synopsis 
iv 
the products exhibited lower antioxidant activity as compared to the reference 
compounds. The synthesized lipoic acid containing phosphatidylcholine derivatives have 
potential in drug delivery research as the lipoic acid is known to be effective in various 
disease conditions, in addition to being an effective antioxidant and biological activities. 
 
Chapter 4: Chemo-enzymatic Synthesis and in vitro Antioxidant and Antimicrobial 
Studies of Phenolic Acid Based-Structured Phosphatidylcholines  
Recent literature reveals that several phospholipids are being synthesized by 
incorporating polyunsaturated fatty acids and unusual fatty acids for specific applications. 
Literature reveals that phenolic acids containing phospholipids are scarce even though 
they may be promising for some novel applications. Phenolic acids are ubiquitous natural 
antioxidants accounting for approximately one third of the phenolic compounds in our 
daily diet. In addition to antioxidant activity, it is reported that phenolic acid derivatives 
exhibit several biological activities. In this chapter, chemo-enzymatic synthesis of twelve 
novel phosphatidylcholines containing phenolic acids (4-hydroxy phenyl acetic, 4-
hydroxy phenyl propanoic, ferulic, sinapic, vanillic and syringic acids) in sn-1 and fatty 
acids in sn-2 position is described for the first time (Scheme 3-7). Initially, hydroxyl 
group of phenolic acids was protected with tert-butyl diphenyl silyl chloride in presence 
of imidazole to obtain 4-(tert-butyl diphenyl silyloxy) phenolic acids in 82-90% yields.  
 
Scheme 3. Synthesis of Protected Phenolic Acids 
Lyso PCs were prepared by enzymatic hydrolysis of DPPC and egg PC in 90-93% 
yields. Lyso PCs were esterified employing N-(3-dimethylaminopropyl)-N′-
ethylcarbodiimide hydrochloride in presence of 4-dimethylaminopyridine with protected 
Synopsis 
v 
phenolic acids to obtain 1-(4-tert-butyl diphenyl silyloxy) phenoyl-2-acyl-sn-glycero-3-
phosphocholines in 48-56% yields. The final step, tert-butyl diphenyl silyl group was 
removed from 1-(4-tert-butyl diphenyl silyloxy) phenoyl-2-acyl-sn-glycero-3-
phosphocholines with tetrabutylammonium fluoride to obtain 1-phenoyl-2-acyl 
phosphatidylcholines in 87-94% yields. The overall yields of the products are in the range 
of 30.8-44.0% from PC.  
 
Scheme 4. Synthesis of 2-Palmitoyl and 2-Acyl Lyso Phosphatidylcholine 
 
 
Scheme 5. Synthesis of Cinnamic Acid Derivatives of Phosphatidylcholine 
 
 
Scheme 6. Synthesis of Benzoic Acid Derivatives of Phosphatidylcholine 
Synopsis 
vi 
 
Scheme 7. Synthesis of Phenolic Acid Derivatives of Phosphatidylcholine 
All the products were characterized by FT-IR, NMR and MS analysis. All the 
compounds were tested for in vitro antioxidant and anti-microbial activities. Among the 
active derivatives, compound 1-(4-hydroxy-3,5-dimethoxy) cinnamoyl-2-acyl-sn-
glycero-3-phosphocholine exhibited excellent antioxidant activity which was higher than 
the standard BHT. Preliminary investigation of antimicrobial evaluation of the prepared 
phenol phospholipids exhibited moderate to good antimicrobial activity on some strains. 
Phenolic phosphatidylcholines may have potential antioxidant activity in variety of food 
matrices. 
 
Chapter 5: Synthesis of Novel Phosphatidylethanolamine-N-phenolic Acid 
Derivatives and their evaluation for in vitro Antioxidant activity 
Several biologically active fatty acids including unusual fatty acids and their 
derivatives were incorporated into several phospholipids at sn-1 and sn-2 positions and 
evaluated for some specific properties. Similarly, a number of studies were reported by 
modifying the head group of PE at amino-functionality. N-acylethanolamines are known 
to exhibit variety of biological activities depending on its acyl chain. N-
Palmitoylethanolamine and N-oleoylethanolamine have been documented as anti-
inflammatory, analgesic and appetite-suppressing substances. N-Acyl phospholipids 
represent an unusual class of phospholipids that contain head groups modified with fatty 
acids. NAPEs play a vital role during injury or stress and also some NAPEs function as 
signaling molecules. Head group modification of phosphatidylethanolamine with fatty 
acids was extensively studied but similar modification with phenolics acids has not 
Synopsis 
vii 
examined so far. In this chapter, eight novel phosphatidylethanolamine-N-phenolic acid 
derivatives were synthesized by modifying the head group of egg PE at amine 
functionality with phenolic acids (4-hydroxy phenyl acetic, 4-hydroxy phenyl propanoic, 
cinnamic, ferulic, sinapic, caffeic, vanillic and syringic acids) for the first time (Schemes 
8 & 9). Initially, hydroxyl group of phenolic acids was protected with tert-butyl diphenyl 
silyl chloride in presence of imidazole to obtain 4-(tert-butyl diphenyl silyloxy) phenolic 
acids in 82-90% yields.  
 
Scheme 8. Synthesis of Protected Phenolic Acid Chlorides 
The resulting 4-(tert-butyl diphenyl silyloxy) phenolic acids were converted into 
4-(tert-butyl diphenyl silyloxy) phenolic acid chlorides which were reacted with 
phosphatidylethanolamine (PE) isolated from egg yolk lecithin in presence of 1,8-
diazabicyclo[5.4.0] undec-7-ene to obtain PE-N-4-(tert-butyl diphenyl silyloxy) phenolic 
acids in 60-79% yields. In the final step, tert-butyl diphenyl silyl group was removed 
from PE-N-4-(tert-butyl diphenyl silyloxy) phenolic acids to obtain PE-N-phenolic acid 
derivatives in 70-85% yields. The overall yields of the products are in the range of 34.4-
60.4% from PE. All the products were characterized by FT-IR, NMR and MS analysis. 
The compounds PE-N-4-hydroxy-3-methoxy cinnamic acid, PE-N-4-hydroxy-3,5-
dimethoxy cinnamic acid and PE-N-3,4-dihydroxy cinnamic acid exhibited excellent 
radical scavenging activity and the EC50 values were found to be lower than the standard 
BHT and α-tocopherols. The compounds PE-N-4-hydroxy-3-methoxy benzoic acid and 
PE-N-4-hydroxy-3,5-dimethoxy benzoic acid also exhibited good antioxidant activities. 
 
Synopsis 
viii 
 
 
Scheme 9. Synthesis of Phosphatidylethanolamine-N-Phenolic Acid Derivatives 
These are novel PE-N-phenolic acid derivatives which may have potential 
applications in the interface of chemistry and biology as existing PE-N-acylated long 
chain derivatives are reported to posses several biological activities. The presence of 
phenolics has to be examined and compared for biological activities that are reported for 
the PE-N-acyl derivatives in order to know the potential of these novel compounds. 
 
 
 


English

Chemo-enzymatic Synthesis of Novel Structured Phospholipids and their Biological Evaluation

MENON, TARA G.

 
 
 
     
         
        
  
      
         
         
     
  
    
     
    
       
        
     
  
   
        
      
        
      
 
        
         
        
      
ABSTRACT
Salinity and drought are the two major environmental constraints that
affect plant growth and in turn crop productivity, a problem that has been
increased by improper land usage and irrigation practices. Thorough
understanding of the salt tolerance adaptations of plants in terms of biochemical
and molecular levels can provide tremendous knowledge about their tolerance
strategies. Salinity stress in plants induces the formation of reactive oxygen
species (ROS) and plants have formulated an array of ROS scavenging system
(enzymatic and nonenzymatic antioxidants) to mitigate the cellular components
from oxidative burst. 
Mangroves are intertidal plants inhabiting the coastal zones of tropical
and subtropical regions and possess unique characteristics of tolerating high-
salinity of seawater and also tidal currents. Recent progresses in understanding
the physiological mechanism of salinity adaptation in mangroves on molecular
level indicate that the phenomenon is indeed tightly linked to the regulation of 
gene expression. Recent studies on salinity tolerance in mangroves like
Avicennia marina, Aegiceras corniculatum, Bruguiera gymnorrhiza, Bruguiera
cylindrica, Ceriops tagal, Acanthus species have identified number of 
differentially expressed stress regulated genes. Rhizophora apiculata Blume. is
a highly salt tolerant mangrove species inhabiting the coastal belts of Kerala.
The present work proposes to examine the ROS cycle and also gene
expression in Rhizophora apiculata in response to NaCl stress by suppression
subtractive hybridization and gene cloning analysis.
Salt stress was imposed on R. apiculata seedlings with five different
concentrations of NaCl (0, 100, 200, 300, 400 and 500 mM) and also with time
slots such as 3, 6, 12 and 24 h durations. NaCl induced remarkable changes in
total protein levels and is visualized with protein banding by SDS-PAGE. NaCl
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stress induced the profile of superoxide anion and hydrogen peroxide content.
Further, the activities of NADPH oxidase, superoxide dismutase (SOD),
catalase (CAT) and peroxidae (GPOX) showed varied levels of expression with
concentrations and durations. Different isoenzyme of SOD, CAT and GPOX
were detected with the NaCl treatment. Enhancement in antioxidant enzyme
activities could be an induced response against cellular damage due to NaCl
stress. Significant ascorbate-glutathione cycle (in terms of activities of 
ascorbate peroxidase (APX), regenerating enzymes and isozymes of APX)
supports the efficiency of the mangrove to detoxify the ROS hydrogen peroxide
from cells. Ascorbate, reduced glutathione and α-tocopherol increase the
capacity of the species to neutralize the toxic effects of NaCl stress.
The molecular part includes Subtractive hybridization using PCR Select
TM Subtraction kit (Clontech, CA, USA). Several stress genes were isolated,
which were then classified to nine functional categories viz., Metabolism,
Protein degradation and folding, Secondary metabolism, Cell rescue and
defense, Transport facilitation, Signal transduction, Transcription and
translation, Photosynthesis and Unclassified genes of unknown function. The
expression patterns of twelve of the genes thus obtained were studied at 6 h,
12 h and 24 h time points of salinity stress using Real time PCR. Most genes
were found to be upregulated under salt stress and showed maximum
upregulation at the 6 h time point. Two of the genes studied were down
regulated after 6 h, implying that the pattern of gene expression varies with time
of application of stress.
The most important gene identified by SSH and upregulated in Real time
RT PCR is Cytochrome P450 monooxygenase (S)-N-methylcoclaurine 3′-
hydrolase (CYP80B3), which acts in the hydroxylation of (S)-N-
Methylcoclaurine to yield (S)-3'-Hydroxy-N-methylcoclaurine.The full length
gene (1.5 Kb) was isolated and its expression in planta was attempted. The
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promoter sequence of the gene was also isolated by genome walking approach.
The size of the amplified product was ~0.5Kb. Several domains were identified
in the promoter region such as CAAT box, TATA box, Myb Binding Site (MBS)
etc.
Another gene that was highly upregulated in the real time PCR analysis
was that of Hevamine A precursor.The gene (1.1Kb) was isolated, cloned into a
binary vector, pMDC 139 and expressed in onion epidermal cells. Syringe
infiltration of the binary vector construct into onion peels showed blue colour
due to gus activity.
The present results suggest that the synergistic effect of different ROS-
scavenging enzymes and compounds effectively improve the biochemical
caliber of plants, thereby reducing the degree of oxidative injuries. Similarly, the
genes and the gene elements thus isolated may be used to confer the trait of 
salt tolerance to non – tolerant genotypes, which can ultimately prove beneficial
for crop improvement programmes.
Key words: Antioxidant enzymes, Mangrove, NaCl, Oxidative stress, Reactive
oxygen species, Rhizophora apiculata, Salinity, Stress genes
xi


MOLECULAR SCREENING FOR SALT TOLERANCE GENES IN Rhizophora apiculata Blume.

Verma, Yogesh Kumar

xi 
 
Synopsis 
The thesis entitled “Synthesis and Application of Spiro-
Cyclopropanecarboxylated Sugars” is divided into four chapters. 
 
Chapter 1 
An Introduction to the chemistry of spiro-cyclopropane- 
carboxylated sugars 
This chapter mainly discuss the synthesis of exo-glycals from different sugar based 
scaffolds and its applications in the synthesis of C-glycosides and carbasugars. exo-glycals are 
very important synthetic intermediates in both carbohydrate synthesis as well as in total 
synthesis of natural products. In addition, they have been versatile starting materials for the 
synthesis of spiro-cyclopropanecarboxylated sugars. This chapter starts with a brief 
introduction about the glycals followed by synthesis of exo-glycals. Different protocols 
available for the incorporation of an exo-olefin on pyranose or furanose moiety are outlined in 
the chapter. Out of several methods for the synthesis of exo-glycals we have chosen two 
methods which have been used in the current research work are Petasis reagent mediated 
conversion of lactones to vinyl ether and 1,8- diazabicyclo[5.4.0]undec-7-ene (DBU) mediated 
dehydrohalogenation reaction.  
Like 1,2-cyclopropanated sugar derivatives, chemistry of spiro-cyclopropanated 
carbohydrate moieties are very important in synthetic organic chemistry. Sugar derived spiro-
cyclopropanes are synthesized by cyclopropanation of the corresponding exo-glycals through 
metal catalysed reactions. Electrophilic ring opening of these donor-acceptor spiro-
cyclopropane carboxylated sugars is a key reaction, applicable to the stereoselective total 
synthesis of various natural products like asteltoxin, pantolactone homolog, eremantholide A. 
Due to the ring strain in cyclopropane ring system these spiro-cyclopropanes acts as 
glycosidase inhibitors, and also useful in the synthesis of spiroketals, bicyclic and tricyclic 
systems. In comparison with endo-glycals, cyclopropanation of exo-glycals is not very much 
explored in the synthetic organic chemistry. To the best of our knowledge, stereoselective 
cyclopropanation of exo-glycals is still an unsolved problem. 
xii 
 
Chapter 2 
Ring-Contraction vs Ring-Expansion Reactions of Spiro-
Cyclopropanecarboxylated Sugars 
 
This chapter mainly describes the electrophilic ring-opening of spiro-
cyclopropanecarboxylated sugars followed by reaction with 1,8- diazabicyclo[5.4.0]undec-7-
ene that revealed an interesting ring-contraction and ring-expansion reactions depending on the 
substrate and the kind of hydroxyl protective group present adjacent to the spiro centre.  A 
stereoselective method for accessing a new class of carbon chain extended keto-furanoses and 
C-glycosylated bicyclic compounds is reported. 
 Spiro-cyclopropanecarboxylated sugar derivatives were prepared by cyclopropanation 
of various sugar derived protected exo-glycals with methyl diazoacetate (MDA) and catalytic 
amount of Rh2(OAc)4 in moderate yields and with good diastereoselectivity. N-
Iodosuccinimide (NIS) mediated ring-opening of these spiro-cyclopropanecarboxylated sugar 
1 (TBS group adjacent to the spirocenter) in dioxane/water provided the α,β-unsaturated ester 
2 in excellent yield. Reaction of 2 with 1,8- diazabicyclo[5.4.0]undec-7-ene in CH2Cl2, at 0 
oC 
gave the ring contracted product 3 in good yield as a single diastereomer. This methodology 
was successfully applied to various sugar derived (pyranose or furanose) spiro-
cyclopropanecarboxylates to provide the corresponding hemiacetals in moderate to good yield 
(Scheme 1). 
 
 
 
Scheme 1: Ring contraction reaction of spiro-cyclopropanecarboxylated sugar. 
 In addition to the ring contraction reaction, ring expansion reaction was also developed 
using fused bicyclic spiro-cyclopropanecarboxylated sugar derivatives. In this protocol 
electrophilic ring opening of the spiro-cyclopropane carboxylate 4 with N-iodosuccinimide 
xiii 
 
dioxane/water provided the ring opened α,β-unsaturated ester 5 which upon exposing to 1,8- 
diazabicyclo[5.4.0]undec-7-ene provided the ring-expanded bicyclic-pyrano[3,2-b]pyran 
derivative  6 as a single diastereomer (Scheme 2). This protocol was also successfully 
implemented to various fused bicyclic spiro-cyclopropanecarboxylated sugar derivatives to 
synthesize the corresponding bicyclic compounds. 
 
 
  
Scheme 2: Ring expansion reaction of fused bicyclic spiro-cyclopropanecarboxylated sugar. 
Chapter 3 
Stereoselective synthesis of 1,6-dioxaspirolactones from spiro-
cyclopropanecarboxylated sugars: Total synthesis of dihydro-
pyrenolide D 
 
 Chapter 3 mainly address the synthesis of a thermodynamically driven stereoselective 
synthesis of 1,6-dioxaspiro[4.n]decan-2-one systems (n = 4, 5) from spiro-
cyclopropanecarboxylated sugar derivatives. The reaction involves a one-pot cyclopropane 
ring opening followed by cyclization to form -spiroketal -lactone moiety. The generality and 
the stereoselectivity of the reaction are examined by synthesizing a series of spirocyclic 
systems.  A successful approach to the synthesis of saturated analogues of pyrenolide D is also 
revealed by the application of the current protocol particularly for the formation of crucial 
quaternary spiro centre of this molecule. These spiro systems are present in number of 
biologically active natural products like pyrenolide D, crassalactone D, epi-crassalactone D, 
cephalosporolide E and F, papyracillic acid A, B and C.  
 Our synthesis depart from fructose derived spiro-cyclopropanecarboxylated sugar 1 
transformed into corresponding carboxylic acid 7 using lithium hydroxide (0.2 N), followed by 
treatment with boron trifluoride diethyl etherate at 0 oC to provide the spiro-lactone 8 as single 
diastereomer in 75% yield respectively (Scheme 3).  
xiv 
 
 
 
 
 
Scheme 3:  Synthesis of spiro-lactone from spiro-cyclopropanecarboxylated sugar. 
 The above strategy was applied to various pyranose and furanose derived spiro-
cyclopropanecarboxylated sugars to give the corresponding spiro-lactones in good yield. 
Further the methodology was extended to the synthesis of dihydropyrenolide D and epi-
dihydropyrenolide D from xylose derived fused bicyclic spiro-cyclopropanecarboxylate 
(Scheme 4). 
 
 
 
Scheme 4: Synthesis of dihydropyrenolide D and epi-dihydropyrenolide D. 
 
Chapter 4 
Synthesis of β-C-Glyco Amino-acids from spiro-
cyclopropanecarboxylated sugars 
 
 Chapter 4 summarizes synthesis of β-C-glycosyl α-amino acids from spiro-
cyclopropane carboxylated sugars. Stereoselective synthesis of 1-C-branched glyco-amino 
acids involving N-iodosuccinimide mediated electrophilic ring opening of spiro-cyclopropane 
carboxylated sugar, followed by conversion of iodide to azide and then Staudinger 
reduction/Zn in acetic acid mediated conversion of azide to amine. Interestingly, some of the 
antibiotics possessing the glyco-amino acid subunit are found to be excellent antibiotics. For 
xv 
 
example, furanose derived glyco-amino acids polyoxins, nikkomycins, and pyranose derived 
glyco-amino acids miharamycins, amipurymicin are some of the anti-biotic molecules isolated 
from bacterial cultures. In addition β-C-glycosidic amino acid structural units are present in the 
synthesis of β-C-galcer, β-C-glucer and its new β-aza-C-glycoside analogues, 
glycospingolipids. These are having in vitro and in vivo natural killer (NK) cell activity. 
 Electrophilic ring opening of spiro-cyclopropanecarboxylated sugar with N-
iodosuccinimide in presence of methanol furnished the ring opened iodo-ketal as mixture of 
diastereomers. Substitution of the iodide with azide followed by removal of OMe with 
triethylsilane in presence of boron trifluoride diethyl etherate followed by reduction of the azide 
to amine using Zn/acetic acid provided the β-D-glycosyl α-amino acids 13 and 14 (Scheme 5). 
Further the developed methodology was extended to glucose and fructose derived spiro-
cyclopropanecarboxylated sugars to furnish the corresponding glyco-amino acids in good 
yield. 
  
 
 
 
Scheme 5: Synthesis of β-C-galactosyl alanines. 


Design and Synthesis of Novel α-Galactosylceramide

Analogs as Immunomodulators and Development of Synthetic Peptide Vaccine

MAITRA, SWATI

Summary	and	Conclusions	
143 
 
 
 
 
 
 
Chapter 8 
SUMMARY AND CONCLUSIONS 
 
 
 
 
 
 
 
 
 
Summary	and	Conclusions	
 
 
144 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Summary	and	Conclusions	
145 
 
 
This study uncovered the critical role two diverse groups of epigenetic regulators such as 
Jumonji domain containing histone lysine demethylases (in particular KDM4/JMJD2 family 
members) and NAD-dependent histone lysine deacetylases (in particular SIRT1 and SIRT2) 
play in mediating the effects of chronic social defeat stress on adult hippocampal 
neurogenesis leading to depression, anxiety and related mood disorders. 
This is first such study where the role of epigenetic regulators such as Sirtuins has been 
uncovered even during the onset of depression and anxiety, i.e. at day 5 of the chronic defeat 
paradigm, in addition to usual 10 days of social defeat stress paradigm, which induces mood 
disorders like phenotype. 
The mood disorders in mouse model appear to be due to the adverse effect of chronic stress 
on the structural plasticity of dentate gyrus neurons, as evident by the analysis of Golgi-Cox 
study. 
10 days of defeat stress led to significant reduction in proliferating neural stem /and or cell 
(NSCs/NPCs) populations in dentate gyrus, as measured by BrdU and Nestin counts in 
C57bl/6 mice and Nestin-GFP transgenic reporter mice, respectively.Chronic stress also led to 
significant decrease in the neuronal differentiation, as evident bytheattenuation of 
doublecortin (DCX) +vecells in DG,the early marker of neuronal differentiation. 
The qPCR, WB, DMOG studies using both in vivo and ex vivo system helped us to conclude 
the crucial role Jmjd2C and Jmjd2Dplayed in mediating the effects of chronic stress on adult 
hippocampal neurogenesis leading to depression, anxiety and related mood disorders. 
This insight also gives us therapeutic strategy for the treatment of mood disorders by 
developing small molecules that can activate these Jmjds or inhibit its epigenetic target 
H3K9me2. 
The other class of epigenetic regulators, NAD+dependent ‘Sirtuins’, in particular few of the 
nuclear sirtuins, also appear to be implicated in our repeated stress-induced depression and 
related mood disorders model. Out of four nuclear Sirtuins, Sirt1 and Sirt2 was found to be 
Summary	and	Conclusions	
 
 
146 
 
dysregulatedin the neurogenic DG both during the onset of depression and also at full-blown 
depression. 
The ex vivo studies using primary neurosphere cultures led us to uncover the crucial role Sirt1 
and Sirt2 play in controlling neurogenesis, i.e. proliferation and differentiation. The level of 
Sirt1 and Sirt2 were opposite to each other; Sirt1 mRNA and protein level was higher in 
proliferating NPCs compared to its level in differentiation stage, whereas Sirt2 mRNA and 
protein level was higher in differentiating phase compared to its level during proliferation. 
Sirt1 acts epigenetically (by deacetylating histone H4K16) and the analysis of chromatin 
immunoprecipitation (ChIP) and qPCR data from the proliferating and differentiating DG 
cultures suggest Sirt1 regulation of a number of gene promoters such as Stat1, Egr3, Dnmt3a 
and E2f1, which play crucial role in controlling proliferation and differentiation, or 
neurogenesis. 
Thus, we report another novel finding i.e. gene targets through which Sirt1 plays its 
epigenetic regulatory function in chronic stress affected neurogenesis and the etiopathology of 
affective disorders. 
The viral-mediated gene targeting experiments using ex vivo as well as in vivo system suggest 
that Sirt2 is also an important player in the etiopathology of mood disorders (although it 
doesn’t work epigenetically). Sirt2 might be acting this by deacetylating the non-histone 
proteins, in particular the tubulin (by regulating its acetylation and hence polymerization), 
crucial for cytoskeletal reorganization that is indispensable for the differentiation of 
NSCs/NPCs. 
Another novel finding we report here is the implication of Sirt6 in the neural stem or 
progenitor cells’ proliferation and differentiation, as shown by our ex vivo experiments. 
The novel outcome of the study on nuclear sirtuins in our diverse models might have 
therapeutic implication. 
Summary	and	Conclusions	
147 
 
Lastly my research effort, together with that of my colleagues and collaborating laboratories, 
resulted in zeroing in onto two novel compounds with remarkable neurotrophic and/or 
neurogenic property and one of these i.e. compound#1 showed great potential for the 
therapeutic development to treat acute ischemic stroke (AIS). 
This was an endeavor to develop epigenetic mechanism based therapeutics development 
where the idea was to identify novel molecules, out of the available compound libraries at our 
institute, and evaluate whether these chemical entities modulate nuclear sirtuins and/or 
histone acetylation. So, using in vitro, ex vivoand in vivo modelswe discovered two interesting 
compounds that not only modulated the levels of Sirtuin 1 and 2, in addition to its role in 
TrkB-MEK-ERK-CREB signaling mechanism, but also showed neuroprotection in AIS 
model.  Further studies will be required to analyze the efficacy of chronic treatment with the 
more neurogenic compound#2 in animal models of diverse brain and behavior disorders 
where the neurogenesis is severely affected, including neurodegenerative disorders and 
psychiatric disorders such as depression and PTSD.  
 
 
 
 
 
 
 
 
 
Summary	and	Conclusions	
 
 
148 
 
 
 
 
 
 
 
 
 
 


EPIGENETIC MECHANISMS IN ETIOPATHOPHYSIOLOGY OF MOOD DISORDERS, WITH REFERENCE TO ADULT NEUROGENESIS

Gupta, Vanika

In Sickness and in Health: Exploring the evolution of immune response using Drosophila melanogaster

Botla, Ganesh

DYNAMIC MODELING AND CONTROL STUDIES FOR A REACTIVE BATCH

DISTILLATION PROCESS

Kumar, Surender

(i) 
 
Synopsis 
Synopsis of thesis entitled “Electrochemical Investigations Related to High Energy Li-O2 
and Li-ion Rechargeable Batteries” by Surender Kumar (4110-112-101-08036) under the 
supervision of Prof. N. Munichandraiah, Department of Inorganic and Physical Chemistry, 
Indian Institute of Science, Bangalore (India), for the Ph.D. degree of the Institute under the 
Faculty of Science.  
A galvanic cell converts chemical energy into electrical energy. Devices that carry 
out these conversions are called batteries. In batteries, generally the chemical components are 
contained within the device itself. If the reactants are supplied from an external source as 
they are consumed, the device is called a fuel cell. A fuel cell converts chemical energy into 
electrical energy as long as the chemicals are supplied from external reserves. The working 
principle of a metal-air battery involves the principles of both batteries and fuel cells. The 
anode of a metal-air cell is stored inside the cell, whereas O2 for the air-electrode is supplied 
from either atmosphere or a tank.  
There are several metal-air batteries available academically, which include Zn-air, Al-
air, Fe-air, Mg-air, Ca-air, Li-air and Na-air batteries. So far, only Zn-air battery is 
successfully commercialized. Li-air battery is attractive compared to other metal-air batteries 
because of its high theoretical energy density (11140 Wh kg
-1
). The energy density of Li-air 
battery is 3 - 5 times greater than state-of-art Li-ion battery. Li-air (or Li-O2) battery 
comprises Li-metal as the anode and a porous cathode. The cathode and the anode are 
separated by a suitable separator soaked in an organic electrolyte. Atmospheric air can enter 
the battery through the porous cathode. Out of the mixture of gases present in the air, only O2 
is electrochemically active. For optimization purpose, most of researchers use pure O2 gas 
instead of air. Li-air battery is not commercialized till now because of several issues 
associated with it. The issues include: (i) sluggish kinetics of O2 electrode reaction, (ii) 
decomposition of the electrolyte during charge-discharge cycling, (iii) formation of Li 
dendrites, (iv) contamination by moisture, etc. Among these scientific and technical problems 
related to Li-O2 cell system, studies on rechargeable O2 electrode with fast kinetics of oxygen 
reduction reaction (ORR) during the cell discharge and oxygen evolution reaction (OER) 
during charge in non-aqueous electrolytes are important. In non-aqueous electrolytes, the 1-
electron reduction of O2 to form superoxide (O2
-
) is known to occur as the first step. 
(ii) 
 
Subsequently, superoxide undergoes reduction to peroxide (O2
2-
) and then to oxide (O
2-
). The 
kinetics of ORR is slow in non-aqueous electrolytes. Furthermore, the reaction needs to be 
reversible for rechargeable Li-air batteries. In order to realize fast kinetics, a suitable catalyst 
is essential. The catalyst should be bifunctional for both of ORR and OER in rechargeable 
battery applications. Noble metal particles have been rarely investigated as catalysts for O2 
electrode of Li-O2 cells. Graphene has two-dimensional planar structure with sp
2
 bonded 
carbon atoms. It has become an important electrode material owing to its high electronic 
conductivity and large surface area. It has been investigated for applications such as 
supercapacitors, Li-ion batteries, and fuel cells. Catalyst nanoparticles prepared and anchored 
to graphene sheets are expected to sustain discrete existence without undergoing 
agglomeration and therefore they possess a high catalytic stability for long term experiments 
as well as applications. In this context, it is intended to explore the catalytic activity of noble 
metal nanoparticles dispersed on reduced graphene oxide (RGO) for O2 electrode of Li-O2 
cells. While a majority of the investigations reported in the thesis involves noble metal and 
alloy particles dispersed on RGO sheets, results on polypyrrole-RGO composite and also 
magnesium cobalt silicate for Li-O2 system are included. A chapter on electrochemical 
impedance analysis of LiMn2O4, a cathode material of Li-ion batteries, is also presented in 
the thesis.      
 Introduction on electrochemical energy storage systems, in particular on Li-O2 system 
is provided in the 1
st
 Chapter of the thesis. Synthesis of Ag nanoparticles anchored to RGO 
and catalytic activity are presented in the 2
nd
 Chapter. Ag-RGO is prepared by insitu 
reduction of Ag
+
 ions and graphene oxide in aqueous phase by ethylene glycol as the 
reducing agent. The product is characterized by powder XRD, UV-VIS, IR, Raman, AFM, 
XPS, SEM and TEM studies. The SEM images show the layered morphology of graphene 
and TEM images confirm the presence of Ag nanoparticles of average diameter less than 5 
nm anchored to RGO (Fig. 1a). Ag-RGO is investigated for ORR in alkaline (1 M KOH), 
neutral (1 M K2SO4) and non-aqueous 0.1 M tetrabutyl ammonium perchlorate in dimethyl 
sulphoxide (TBAP-DMSO) electrolytes. The ORR follows 4e
-
 reduction in aqueous and 1e
-
 
reduction pathway in non-aqueous electrolytes. Li-O2 cells are assembled with Ag-RGO as 
 
 
(iii) 
 
 
  
 
   
 
 
  
 
Fig. 1. (a) TEM image of Ag-RGO and (b) charge-discharge voltage profiles of Li-O2 (Ag-RGO) 
cells. 
oxygen electrode catalyst in non-aqueous electrolyte (1 M LiPF6-DMSO) and subjected to 
charge-discharge cycling at several current densities. The discharge capacity values obtained 
are 11950 (11.29), 9340 (5.00), and 2780 mAh g
-1
 (2.47 mAh cm
-2
) when discharged at 0.2, 
0.5, 0.8 mA cm
-2
, respectively (Fig. 1b). Powder XRD studies of discharged electrodes 
indicate the formation of Li2O2 and Li2O during the cell discharge. In addition to these 
studies, Na-O2 cells are also assembled with Ag-RGO in non-aqueous electrolyte. It is 
concluded that the chemistry Li-O2 and Na-O2 cells are similar except for the capacity 
values.  
 Metal nanoparticles of Au, Pd and Ir are decorated on RGO sheets by reduction of 
metal ions on graphene oxide by NaBH4. Au-RGO, Pd-RGO and Ir-RGO are characterized 
by various physicochemical techniques. Particle size of metal nanoparticles ranges from 2 to 
 
 
 
 
  
 
 
 
 
 
 
 
Fig.2. Charge-discharge voltage profiles Li-O2(RGO) (i) and Li-O2(Au-RGO) (ii) cells at current 
density 0.3 mA cm
-2
. 
0 2500 5000 7500 10000 12500 15000
1.5
2.0
2.5
3.0
3.5
4.0
4.5 0.2 mA cm-2
C
e
ll
 v
o
lt
a
g
e
 /
 V
Capacity / mAh g
-1
(i) 0.2 mA cm
-2
(b)
 
 
0.5 mA cm
-2
(ii) 0.5 mA cm
-2
0.8 mA cm
-2
 
 
(iii) 0.8 mA cm
-2
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
(ii)
(i)
C
e
ll
 v
o
lt
a
g
e
 /
 V
(i) (ii)
0 500 1000 1500 2000 2500 3000
2.15 mAh cm-2
1.23 mAh cm-2
1.70 mAh cm-2
3.35 mAh cm-2
Specific capacity / mAh g-1
 
a
(iv) 
 
10 nm on graphene sheets. All samples are studied for ORR in aqueous and non-aqueous 
electrolytes by cyclic voltammetry and rotating disk electrode experiments. Li-O2 cells are 
assembled in 1 M LiPF6-DMSO and discharge capacity values obtained are 3344, 8192 and 
11449 mAh g
-1
 with Au-RGO, Pd-RGO and Ir-RGO, respectively, at 0.2 mA cm
-2
 current 
density. The results of these studies are described in Chapter 3.    
 
 Synthesis and electrochemical activity of Pt-based alloy nanoparticles (Pt3Ni, Pt3Co 
and Pt3Fe) on RGO are presented in Chapter 4. The Pt3Ni alloy particles are prepared by 
simultaneous reduction of Pt
4+
, Ni
2+
 and graphene oxide by hydrazine in ethylene glycol 
medium. Pt3Co-RGO and Pt3Fe-RGO are also prepared similar to Pt3Ni-RGO. Formation of 
alloys is confirmed with XRD studies. O2 reduction reaction on Pt-alloys in non-aqueous 
electrolyte follows 1e
-
 reduction to O2
-
. RDE results show that Pt3Ni-RGO is a better catalyst 
than Pt for O2 reduction (Fig. 3). Li-O2 cells are assembled with all samples and subjected to    
 
  
 
 
  
 
 
 
 
 
 
 
 
Fig. 3. Linear sweep voltammograms of Pt3Ni-RGO, Pt3Co-RGO and Pt3Fe-RGO in 0.1 M TBAP-
DMSO with 1600 rpm at 10 mV s
-1
 scan rate. The area of GC electrode was 0.0314 cm
2
 with a 
catalyst mass of 200 µg.  
 
charge-discharge cycling at several current densities. The initial discharge capacity values 
obtained are 14128, 5000 and 10500 mAh g
-1
 with Pt3Ni-RGO, Pt3Co-RGO and Pt3Fe-RGO, 
respectively, as the air electrode catalysts.  
 Polypyrrole (PPY) is an attractive conducting polymer with advantages such as high 
electronic conductivity and electrochemical stability. A combination of advantages of 
graphene and PPY composite are explained in the Chapter 5. PPY is grown on already 
synthesized RGO sheets by oxidative polymerization of pyrrole in an acidic medium. RGO-
-2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4
-1.4x10
-4
-1.2x10
-4
-1.0x10
-4
-8.0x10
-5
-6.0x10
-5
-4.0x10
-5
-2.0x10
-5
0.0
2.0x10
-5
C
u
rr
e
n
t 
/ 
A
Potential / V vs SHE
(i)
(ii)
(iii)
(i) Pt3Fe-RGO
(ii) Pt3Co-RGO
(iii) Pt3Ni-RGO
+
(v) 
 
2 4 6 8 10 12 14 16
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
(i) Charge voltage
(ii) Discharge voltage
(ii)C
e
ll
 v
o
lt
a
g
e
 /
 V
Cycle number
(b)
(i)
0 200 400 600 800 1000
1.5
2.0
2.5
3.0
3.5
4.0
4.5
C
e
ll
 v
o
lt
a
g
e
 /
 V
Specific capacity / mAh g
-1
(a)
PPY composite is characterized by XRD and Raman spectroscopy studies. Li-O2 cells are 
assembled in non-aqueous electrolyte and subjected for charge-discharge cycling at different 
current densities. The discharge capacity value of Li-O2(PPY-RGO) cell is 3358 mAh g
-1
 
 
 
 
   
 
 
 
 
Fig. 4. (a) Discharge-charge performance of Li-O2(PPY-RGO) cell with a current density of 0.2 mA 
cm
-2  
limiting to a capacity of 1000 mAh g
-1
 and (b) variation of cut-off voltages on cycling. 
(3.94 mAh cm
-2
) in the first cycle. Li-O2(PPY-RGO) cell delivers 3.7 times greater discharge 
capacity than Li-O2(RGO) cell. Cycling stability of Li-O2 (PPY-RGO) cell is investigated by 
charge-discharge cycling by limiting the capacity to 1000 mAh g
-1
, and the cell voltage at the 
end of discharge and at the end of charge are found constant at 2.75 and 4.10 V, respectively 
(Fig. 4 a, b). This study shows that PPY-RGO is stable in Li-O2 cells. Electrochemical 
impedance study shows that charge-transfer resistant is 500 Ω for freshly assembled Li-
O2(PPY-RGO) cell and it decreases to 200 Ω after 1
st
 discharge.  
 Synthesis of magnesium cobalt silicate and its electrochemical activity are presented 
in Chapter 6. MgCoSiO4 is synthesized by mixed solvothermal approach and characterized 
by various physicochemical techniques. Cubic shaped MgCoSiO4 is investigated for oxygen 
evolution reaction (OER) activity in alkaline and neutral media. The current values at 0.95 V 
versus SHE are 43, 0.18, 16 mA cm
-2
 on MgCoSiO4, bare carbon paper and Pt foil 
electrodes, respectively (Fig. 5), indicating that MgCoSiO4 is a good catalyst for OER. The 
onset potential for OER is 0.68 V versus SHE on MgCoSiO4 in 1 M KOH. OER activity on 
MgCoSiO4 is also studied in K2SO4 and phosphate buffer electrolytes. The results indicate 
good catalytic activity of MgCoSiO4 in neutral electrolytes also. The catalytic activity of 
 
(vi) 
 
 
 
 
 
  
 
 
 
Fig. 5. Cyclic voltammograms of bare carbon paper (i), Pt foil (ii), MgCoSiO4 coated carbon (iii) 
electrodes in 1 M KOH (sweep rate = 5 mV s
-1
, loading level = 1.15 mg, area = 0.5 cm
-2
). 
MgCoSiO4 towards ORR in aqueous and non-aqueous electrolytes is studied by RDE 
experiments. Li-O2 cells are assembled with bifunctional MgCoSiO4 catalyst in 1 M LiPF6-
DMSO electrolyte and the discharge capacity values obtained are 7721 (8.27), 2510 (1.66) 
and 1053 mAh g
-1
 (0.92 mAh cm
-2
) when discharged at 0.3, 0.5 and 0.8 mA cm
-2
 current 
densities, respectively.       
Electrochemical impedance spectroscopy (EIS) measurements of LiMn2O4 electrode 
are carried out at different temperatures from -10 to 50 
0
C and in the potential range from 
3.50 to 4.30 V, and the data are analysed in Chapter 7.  In the EIS spectra recorded over the 
frequency range from 100 kHz to 0.01 Hz at different temperatures, there are two semicircles 
present in the Nyquist plot (Fig. 6a). But in 3.90 to 4.10 V versus Li/Li
+
(1M) potential range 
at low temperatures (-10 to 15 
o
C) range, another semicircle also appears (Fig. 6b). 
Impedance parameters such as solution resistant (Rs), charge-transfer resistance (Rct), double-
layer capacitance (Cdl), electronic resistance (Re) and Warburg impedance (WR), etc., are 
obtained by analysis of the EIS data. The variations of resistances with temperature are 
analysed by Arrhenius-like relationships and the apparent activation energies of the 
corresponding transport properties are evaluated. The values of activation energy for charge-
transfer process are 0.37, 0.30 and 0.42 eV, at 3.50, 3.90 and 4.10 V versus Li/Li
+
(1M), 
respectively.  The chemical diffusion coefficient of Li
+
 ions into LiMn2O4 calculated from 
EIS data. The values of diffusion coefficient calculated are in the range of 2.50 x 10
-12
 - 4.10 
x 10
-11
 cm
2
 s
-1
.  
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0
10
20
30
40
50
(iii)
(ii)
C
u
rr
e
n
t 
d
e
n
s
it
y
 /
 m
A
 c
m
-2
Potential / V vs SHE
(i)
+
 
 
(vii) 
 
0 400 800 1200 1600 2000 2400
0
-400
-800
-1200
-1600
-2000
-2400
 Z
"
 /
 
Z' / 
100k
10m
31.6m
125.8
 
 
(a)
0
-100
-200
-300
-400
-500
-600
0 100 200 300 400 500 600
Z
"
 /


Z' /  
10m63m1.9
25.1
100
100K
(b)
 
 
 
 
 
 
 
 
Fig. 6. Nyquist plot of impedance study of Li/LiMn2O4 cell at 3.50 V (a) and 3.90 V (b) at -10 
0
C. 
 
Details of the above studies are described in the thesis. 
 
 
 
 


Electrochemical Investigations Related to High Energy Li-O2 and Li-ion Rechargeable Batteries

Voggu, Rekha

SELECTIVE CATALYTIC HYDROGENOLYSIS OF GLYCEROL TO 1,2-PROPANEDIOL

Mehta, Gunjan

Page | 1  
 
Abstract 
Cell division is a fundamental process required for the propagation of life. It 
takes place either by mitosis (equational genome segregation) or meiosis (reductional 
genome segregation). This study deals with two important players of the genome 
segregation machinery, kinetochore and cohesin, using Saccharomyces cerevisiae as a 
model system.  
Kinetochore is a multiprotein complex required for connecting centromeres to 
the microtubules for the segregation of the chromosomes. Any defect in kinetochore 
assembly results in weak connections between centromere and microtubule, leading to 
the missegregation of chromosomes. In budding yeast, kinetochore is made up of 
around 100 proteins, categorized into eight complexes, which are further categorized 
as inner, central and outer complexes based on their relative position on the centromere-
microtubule interface. Ctf19 supercomplex, one of the central kinetochore complexes, 
is made up of biochemically distinguishable three subcomplexes: COMA, Iml3-Chl4, 
and Ctf3. However, the functional significance of each of these subcomplexes of Ctf19 
supercomplex is not known. In the first objective of this thesis, the main goal is to 
identify the significance of the COMA and the Iml3-Chl4 subcomplexes in meiosis. 
Systematic chromosome segregation analysis and meiotic progression analysis in the 
wild-type and the mutants of the COMA and the Iml3-Chl4 subcomplexes revealed 
their functional significance during meiosis, although they were found to be redundant 
during mitosis. The COMA subcomplex is epistatic to the Iml3-Chl4 subcomplex 
because absence of the COMA subcomplex proteins generates severe defects in 
comparison with iml3Δ or chl4Δ. Interestingly, meiotic progression analysis 
demonstrated that Ctf19 complex mutants arrest transiently during prophase I and 
metaphase I, indicating their importance during these stages of meiosis. Therefore, we 
aimed to observe the role of Ctf19 in executing different events of meiosis I (MI). 
In the second objective of this thesis, effects of absence of Ctf19 in various MI 
specific events were observed. Cell biological and biochemical analysis suggested 
impairment of many MI specific events, such as pairing of homologous chromosomes, 
bi-orientation of homologous chromosomes, mono-orientation of sister kinetochores, 
chiasmata resolution, sister chromatid cohesion and chromosome condensation, in 
absence of Ctf19. 
As the absence of Ctf19 affects meiosis severely than mitosis, we asked the 
question whether the absence of Ctf19 affects the kinetochore organization severely  
Page | 2  
 
during meiosis in comparison with mitosis. In the third objective of this thesis, live cell 
imaging and chromatin immunoprecipitation based experiments suggest that the 
faithful organization of the meiotic kinetochore depends more on Ctf19 in comparison 
with the mitotic kinetochore, as absence of Ctf19 failed to recruit many complexes at 
the centromere during meiosis, but not in mitosis. 
The fourth objective of this thesis deals with the cohesin biology to reveal the 
mechanism of stepwise loss of cohesin during meiosis. Preliminary cell biological 
analysis has been carried out to find out the interdependencies among Sgo1, PP2A and 
Spo13, key protectors of the centromeric cohesin, for their involvement in the 
protection of centromeric cohesin during MI. Our data suggests that Spo13 and 
Sgo1/PP2A act through independent pathways for the protection of centromeric 
cohesin. Although Sgo1 and PP2A have been shown to be involved in the same pathway 
for the protection of centromeric cohesin during meiosis I, sgo1Δ and rts1Δ (PP2A 
mutant) mutants do not show similar quantity of cohesin defect, suggesting that PP2A 
is involved in some but not all the functions of Sgo1 for the protection of centromeric 
cohesin. Additionally, there are several hypotheses regarding the mechanism of 
deprotection of centromeric cohesin during meiosis II (MII). Here, an attempt was made 
to test one such hypothesis, whether increased distance between cohesin (Rec8) and its 
protector (Sgo1) during MII is required for the deprotection of centromeric cohesin. We 
designed FRET-based analysis to observe the proximity between cohesin and its 
protector (Sgo1) during MI and MII, but due to limitations of the FRET approach, it 
failed to provide conclusive information. 
In summary, this work provides significant insight into the essential process of 
life, i.e. cell division. It increases the basic understanding of meiosis, the process 
required for the generation of sperm and egg cells in the human, which has a significant 
impact on human fertility and public health. 
 
 
 
 
 
 


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Chemo-enzymatic Synthesis of Novel Structured Phospholipids and their Biological Evaluation

MOLECULAR SCREENING FOR SALT TOLERANCE GENES IN Rhizophora apiculata Blume.

Design and Synthesis of Novel α-Galactosylceramide Analogs as Immunomodulators and Development of Synthetic Peptide Vaccine

EPIGENETIC MECHANISMS IN ETIOPATHOPHYSIOLOGY OF MOOD DISORDERS, WITH REFERENCE TO ADULT NEUROGENESIS

In Sickness and in Health: Exploring the evolution of immune response using Drosophila melanogaster

DYNAMIC MODELING AND CONTROL STUDIES FOR A REACTIVE BATCH DISTILLATION PROCESS

Electrochemical Investigations Related to High Energy Li-O2 and Li-ion Rechargeable Batteries

SELECTIVE CATALYTIC HYDROGENOLYSIS OF GLYCEROL TO 1,2-PROPANEDIOL

Functional characterization of the kinetochore complex Ctf19 and the mechanism of cohesin disassembly in meiosis using Saccharomyces cerevisiae

Sulfenylation of H-Phosphonates, H-Phosphonites, Phosphine Oxides, Indoles and Synthesis of substituted (benzofuran-yl)- aryl chiral carbinols.

506

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