373 research outputs found
Bibliographics for the 983 eprints in the live archives of E-LIS : trends and status report up to 7th July 2004, based on author-self-archiving metadata
No full textThe priority for ideas and philosophy related to "Network Theory" have been traced back and documented by Braun(2004),and credit goes to Karinthy(1929).The IT has empowered to realise it, as the most practical phenomena and it is no more a humour. The OAI (Open Archives Initiatives)and ACIS (Academic Contributor Information System)are progressive in the direction ,which may lead to realise the "Collective Genius" at global level. Focus of present study is on Author-Self-Archiving (A-S-A)Metadata of the 983 Eprints in the Live Archives of the E-LIS (EPrints of Library and Information Science),which were approved till 7th July 2004.The A-S-A Metadata was used for librametric analysis. Self-explanatory bibliographics are illustrated.The highlights include: Conference papers (34%); highest approval, June 2004 (28%); published archives (76%);not refereed (52%); not in public domain (60%); highest self-archiving-author (De Robbio, Antonella).The Nos. of EPrints having single JITA domain specifications were: Theoretical and general aspects of libraries and information(27); Information use and sociology of information(80);Users,literacy and reading(13);Libraries as physical collections(30);Publishing and legal issues(57);Management(13);Industry, profession and education(36);Information sources, supports, channels(113) ; Information treatment for information services, Information functions and techniques (101); Technical services libraries, archives and museums(25); Housing technologies(1); Information technology and library technology(92); and Inter-domainery (395) i.e. having specifications of two or more than two JITA classes
Polynomial energy decay rate and strong stability of Kirchhoff plates with non-compact resolvent
No full textUsing a direct approach, we establish the polynomial energy decay rate for smooth solutions of the equation of Kirchhoff plate. Consequently, we obtain the strong stability in the absence of compactness of the resolvent of the infinitesimal operator. © Birkhäuser Verlag, 2005.Alabau F, 2002, J EVOL EQU, V2, P127, DOI 10.1007-s00028-002-8083-0; ARENDT W, 1988, T AM MATH SOC, V306, P127; BATKAI A, IN PRESS MATH NACHR; BENCHIMOL CD, 1978, SIAM J CONTROL OPTIM, V16, P373, DOI 10.1137-0316023; Brezis H., 1992, ANAL FONCTIONELLE TH; GIBSON JS, 1980, SIAM J CONTROL OPTIM, V18, P311, DOI 10.1137-0318022; HORN MA, 1994, J MATH SYSTEMS ESTIM, V4, P39; HUANG FL, 1985, J DIFFER EQUATIONS, V104, P307; Komornik V., 1994, EXACT CONTROLLABILIT; Lagnese J. E., 1989, SIAM STUDIES APPL MA; LASIECKA I, 1990, APPL MATH OPT, V21, P167, DOI 10.1007-BF01445162; Lebeau G, 1996, MATH PHYS S, V19, P73; Lions J.-L., 1968, PROBLEMES LIMITES NO, VI; LITTMAN W, 1987, P COMCOM WORKSH MONT; LIU Z, IN PRESS Z ANGEW MAT; Loreti P, 2003, CR MATH, V337, P531, DOI 10.1016-j.crma.2003.08.009; Pazy A, 1983, SEMIGROUPS LINEAR OP; RAO BP, 1993, NONLINEAR ANAL-THEOR, V20, P605, DOI 10.1016-0362-546X(93)90023-L; Rao BP, 1998, SIAM J CONTROL OPTIM, V36, P148, DOI 10.1137-S0363012996300975; RUSSELL DL, 1993, J MATH ANAL APPL, V173, P339, DOI 10.1006-jmaa.1993.1071; RUSSELL DL, 1975, J DIFFER EQUATIONS, V19, P344, DOI 10.1016-0022-0396(75)90009-1; Slemrod M., 1989, Mathematics of Control, Signals, and Systems, V2, DOI 10.1007-BF02551387; WEHBE A, 1998, PITMAN RES NOTES MAT, V383, P174; WEHBE A, 1998, THESIS U L PASTEUR S77
Bio-chemical and Technological investigations on tea
No full textCh. 1. INTRODUCTION AND REVIEW OF LITERATURE
In this Chapter a brief introduction is presented followed by the status of Indian tea industry, processing, tea quality, determination, isolation and identification of quality indicators and health benefits. The review of literature covers aspects relating to the chemical composition, quality co-relation and bioactivities in health benefits of teas as well as objectives and scope of the research work. Besides, the general pathway of biogenesis leading to the volatile aromatic compounds present in the tea have also been discussed. The brief account is given below.
Sheng Nung the chinese emperor (2737 B.C.) was the first to recognize the stimulant effect of tea. Tea is one of the important agro-industrial plantation crops of India. Tea is the beverage with which most of the Indians start their day. The recent research findings indicative of several health benefits have further popularized tea as a beverage. During the year 2007, India produced 945 million kg of tea from 38,705 gardens spread over an area of 4, 35, 057 ha. Out of this, domestic consumption accounts for 76 per cent and exports accounts for 24 per cent.
Tea plant belongs to the Camellia species of Theaceae family. The two basic varieties are recognised namely chinese variety Sinensis and Assamese variety - Assamica. The commercially grown tea plant is highly heterogenous. Tea flush contains polyphenols, amino acids, organic acids, polysaccharides, lipids, carotenoids, caffeine, chlorophylls, minerals and volatiles. The polyphenols which includes catechins constitute 25-30% of the fresh flush on dry 2
weight basis. These are converted to theaflavins, thearubigins, theaflavic acids and bisflavanols during the manufacture of black teas and these are responsible for colour, briskness, brightness and astringency. Theaflavins are determined qualitatively and quantitatively whereas quantitative determination of thearubigins has been possible tentatively but their structures are yet to be explored exhaustively. Caffeine is the major alkaloid present in tea and it is responsible for stimulating action. Highly efficient HPLC method to determine soluble caffeine is reported from this laboratory. Carbohydrates play an important role in the formation of tea aroma. Lipid concentration increases with the maturity of the leaves and is responsible for the formation of C6 volatiles during the manufacture of black tea.
Three types of organic acids are present in tea viz., dicarboxylic acids, fatty acids and monocyclic acids. Monocyclic acids (eg. Quinic and Shikimic) are the precurors of polyphenols. Chlorophyll a and b are reported to be present in the tea and are converted to phaeophytins which are responsible for black colour of commercial tea. ß-carotene is the major compound among the carotenoids and degrades to character impact volaitle compounds such as theaspirone, ß-ionone and related compounds. Although K (Potassium) is the major mineral found the Cu (Copper) and Al (Aluminium), are important for the colour and taste of brewed teas.
Theanine is the most abundant amino acid and accounts for 50% of the total amino acids and 1% of the dry weight of tea. Theanine is a constituent of the "thearabigin" fraction while glutamic acid and ethylamine are its precursors. Amino acids and glucose interact with tea polyphenols during thermal processing and yield coloured moieties and Amadori products, which improve the flavour of tea.
Catechins, theaflavins and thearubigins contribute to the bitterness, astringency, brightness and total colour of black tea infusion. Further thearubigins are responsible for body and richness of the tea brew. Theaflavin digallate is having lowest threshold value for the astringency. Caffeine contributes towards the bitter taste in tea. Characteristic umami or brothy taste of
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black teas is due to the presence of amino acids. The ionone related aroma compounds such as theaspiranes are formed from carotenoids and they are found to have different odour properties. The aroma quality of tea with respect to theaspiranes is yet to be exploited.
Volatile flavour compounds (VFC) play a major role in detemining the unique flavor of tea. Although >600 compounds are reported but the unique composition for character impact aroma of black tea is not yet established. The aroma quality of black teas with respect to the VFCs is measured by different ratios/indices viz., Terpene index, Wickremasinghe-Yamanishi ratio, Mahanta ratio, Yamanishi-Botheju ratio. Wickremasinghe-Yamanishi ratio is the ratio of sum of the peak areas of compounds eluting before linalool to the sum of the peak areas linalool plus all compound that elute after linalool. Smaller the ratio better is the quality. Mahanta ratio is the sum of the peak areas of terpenoids to non-terpenoids. Yamanishi-Botheju ratio is the ratio of peak area of linalool to E-2-hexenal. All the three ratios mentioned above have limitations for their applicability.
Another aroma quality indicator called flavour index (F.I.), the ratio of VFC II to VFC I is reported for kenyan clonal black teas and F.I. is positively correlated to tasters evaluations. This confirms that F.I. is a good aroma quality indicator for Kenyan black teas. However, it should only be used qualitatively since the olfactory perception limits of individual VFC are different. A suitable ratio for Indian black teas with reference to aroma and quality is yet to be explored and the limitation is vide variation in weather. A new approach in terms of novel quality index for tea through the present work has been innovated (chapter 2).
Tea is a good source of flavanoid antioxidants which has a role in prevention of cancer and coronary heart diseases. Tea is known to improve blood flow, eliminate alcoholic toxins, relieve joint pains and acts as a diuretic and improves resistance to diseases.
Flavonoids present in tea can effectively stabilize free electrons through several mechanisms viz., delocalisation of electrons, formation of intramolecular hydrogen bonds and rearrangement of their molecular structure. This may be
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the reason for their antioxidant property. The catechins ranked depending on their antioxidant potential as ECG > EGCG > EC > GC > EGC > C. Theaflavins and thearubigens inhibited the formation of TBARS and these are more effective than vitamin E, glutathione, vitamin C and synthetic phenolic antioxidants. Catechins were also found to be the scavengers of peroxynitrites which are capable of oxidising LDL.
Theaflavins and catechin gallates are more effective scavengers of aqueous and lypophilic stable radicals than many other flavonoids and many antioxidant vitamins. The inhibition mechanism of tea flavonoids is independent of metal ion chelation properties.
Tea flavonoids were found to reduce oxidative damage in animals from radiation, chemical oxidants, diet stress. Drinking of tea beverage was shown to reduce oxidative biomarkers in chronic smokers. Tea was found to reduce the metabolism of compounds to known carcinogens and enhance their detoxification. Thus it is claimed to inhibit variety of cancers such as oesophagal, gastrointestinal, lung and skin cancers.
A cup of black tea is reported to be three times and two times more effective than one serving of common vegetables and one serving of common fruits respectively.
Ch. 2. PROFILING OF INDIAN BLACK TEAS
This chapter describes analytical determination of volatiles and non-volatiles by different methods for profiling Indian black teas. Chromatographic techniques for separation and their determination using spectroscopic techniques besides flavour indices have also been discussed and the quality co-relation on the scientific basis is discussed.
Indian teas especially Darjeeling, Assam and Nilgiris are valued world over for their superior aroma and taste.
In order to improve our scientific understanding on objective tea quality and thereby to help retain supremacy in the world tea trade, it was proposed to
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make an in depth study to generate fingerprint profile of teas grown in different regions of India which ultimately may result in a database with respect to volatile flavour compounds (VFC) as well as non volatile flavour compounds (NVFC) which are responsible for aroma, taste and quality of tea.
Novel approach for overall quality based on Seasonal, regional variations and bio-chemical quality fingerprint
A study was carried on tea samples collected from nine regions spread over four seasons. Profiling of the black tea samples from four seasons (S1=April-June), (S2=July-Sept.), (S3=Oct.-Dec.) and (S4=Jan.-March) based on bio-chemical fingerprint was accomplished.
The brief of the research findings is given below:
Codes for Region / Grade / Garden
Region / Grade / Garden
Code
Tamilnadu, Parajulie
A
Tamilnadu, Pandiar
B
Darjeeling Medium
C
Darjeeling Premium
D
Assam AFTL
E
Assam Magor
F
Nilgiris HG
G
Dooars, Aibheel
H
Dooars, Chinchula
I
Palampur G1
J
Nilgiris HG-CTC
K
Dibrugarh, Rose kandy
L
Palampu G2
M
Assam, Cachar best
N
Assam, Cacher Med.
O
Darjeeling, Kurti
P
Assam BOP
Q
Nilgiris Waynad
R
Annamalai
S
Assam OP
T
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Seasonal variation of TF/TR ratio over tea producing region/grade and quality
The TF content of a tea or the ratio TF/TR is considered to be a good quality indicator of tea. Accordingly seasonal variations of TF/TR ratios over the coded tea producing regions / grades in all the four seasons (s1, s2, s3, s4) were studied. The teas having TF/TR ratios up to 0.04, >0.04-0.08 and >0.08 can be considered to be a good, better and best quality indicator of tea quality respectively. Teas from the region/grade A-I are the better (TF/TR ratios >0.04-0.08) to best (TF/TR ratios >0.08) quality teas over all the four seasons except for the teas from region A, C, D (s1), which fall under good quality category considering their TF/TR ratios (upto 0.04).
Also the teas from region/grade K-L (s2), N,O (s1), PQ (s3) and RS (s4) are the better (TF/TR ratios >0.04-0.08) quality teas except for the teas from region J (s2), M(s3) and T(s4) teas, which fall under good quality category considering their TF/TR ratios (upto 0.04).
The teas from region/grade JKL (s1, s3), M –T (s2), ORST (s3), MP (s1), Q (s4) are also falling under good quality category teas, considering their TF/TR ratios (upto 0.04).
Seasonal variation of sum of Yamanishi-Botheju and Mahantha ratio over tea producing region/grade and tea quality
The VFC (Volatile Flavour Compounds) content of a tea or the sum of the VFC ratios (Yamanishi-Botheju ratio and Mahanta ratio) is considered to be a good quality indicator of tea. Accordingly seasonal variations of or the sum of the VFC ratios (Yamanishi-Botheju ratio and Mahanta ratio) over the coded tea producing regions / grades in all the four seasons (s1, s2, s3, s4) were studied. Accordngly based on the sum of the VFC ratios (i.e.Yamanishi-Botheju ratio and Mahanta ratio) the teas can be categorized as a good (upto 1), better (>1-4) and best (>4) quality indicator of tea respectively.
The teas from regions/grade A-J (all seasons) have better (>1-4) to best (>4) quality as indicated by sum of the VFC ratios (i.e.Yamanishi-Botheju ratio and Mahanta ratio) except for teas from regions/grade AEFHIJ(s2),K-T (s2),
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BDFHIJ(s1), BIJ(s3) which are good (upto 1) quality teas, as indicated by sum of the two VFC ratios. Also the teas from regions/grade M (s3), O (s1), P (s3), RST (s4) are good (upto 1) quality teas as indicated by sum of the two VFC ratios.
Seasonal variation of Borse-Rao quality index over tea producing region/grade and tea quality
A new approach in terms of novel quality index for tea has been innovated through present work and the results are presented. The sum of TF/TR ratios of tea and the sum of the VFC ratios (Yamanishi-Botheju ratio and Mahanta ratio) added together is proposed for the first time as a new and novel quality index, hence forth referred to as Borse-Rao quality index, considered to be an overall quality indicator of tea as both the non-volatiles/volatiles are given due consideration in this quality index. Accordingly seasonal variations of the Borse-Rao quality index over the coded tea producing regions / grades in all the four seasons (s1, s2, s3, s4) were studied. Based on the the Borse-Rao quality index teas can be categorized as a good (upto 1), better (>1-4) and best (>4) quality tea respectively.
The teas from regions/grade having Borse-Rao quality index more than four are C (s2, s4), D (s3, s4), G (s1, s2, s3), H (s3) and I (s4) are the best (>4) quality teas.
The teas from regions/grade having Borse-Rao quality index ranging from one to four are A (s1, s2, s3, s4), B (s2, s3, s4), C (s1, s3), E( s3, s4), F( s3, s4), H (s2, s4), I (s3, s4), J(s2), M (s3) and RS (s4) and indicate that these are better (>1-4) quality teas.
The rest of the teas from regions/grade having Borse-Rao quality index upto one are good quality teas which are BDFH (s1), EF (s2), I (s1, s2), JKL (s3), K-T (s2) and P-T (s3).
The profile of Indian black teas in terms of a bio-chemical fingerprint is carried out in present study which will not only help in understanding the intrinsic 8
quality objectively but also help in tracing the origin of the teas based on the markers identified.
For the first time a novel approach has been evolved to mark teas on the basis of TF/TR ratio, VFC ratios and a novel tea quality index (Borse-Rao quality index) is proposed which takes both volatiles and non-volatiles into account.
Ch. 3. FUNCTIONAL INGREDIENTS FROM UNUSED GREEN TEA LEAVES:
ACTIVITY AND APPLICATIONS
Despite several reports on the radical scavenging activity of green tea from two leaves and a bud, the radical scavenging activity of green tea from coarse and pruned leaves in particular is not studied. The pruned and coarse tea leaves are tea plantation waste, India is one of the largest producers of tea. Therefore, testing of its radical scavenging properties is of interest primarily in order to find new promising sources for natural antioxidants. In this chapter novel approach for preparation of the green teas from the pruned or coarse tea leaves and optimization of extraction conditions to obtain catechin rich radical scavenging conserve and its application with the following two objectives is presented.
1.
To isolate active conserves from coarse and pruned green tea leaves.
2.
To use the active conserves for food applications
Processes for utilization of pruned/coarse green tea leaves (a plantation waste) have been worked out. A novel process for green tea preparation has been standardized and patented.
Processes for isolation, fractionation and enrichment (50-70 % catechin) and separation of radical scavenging conserve (90-94% RSA @ 10-15 ppm) from pruned/coarse green tea leaves have been standardized and patented.
Application of this catechin-rich radical scavenging conserve in nutraceutical ice-cream and cookies was worked out and patented.
The details of the study are presented in the following paragraphs:
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Normal, coarse and pruned fresh tea leaves (low grade) were procured and subjected to enzyme inactivation using cross flow dryer (80-120oC, 4 – 8h), and continuous infra red dryer (70-120oC, 0.5-1.5h) at different temperature and time intervals. The chemical parameters are found to be in the following range, Caffeine (1.30-3.20%); Total polyphenols (11.5-15.5%). Sensory characteristics were found to be similar to that of the commercial green tea samples.
Forty four compounds have been identified from the volatiles of green teas by comparing the mass spectra as well as retention indices reported in literature, followed by retention times of the GC peaks with those of reference compounds run under identical conditions where ever possible. The broad classification of the compounds identified includes ten terpenoids, three aromatic compounds, eight alcohols, seven aldehydes, four acids, eight esters and four compounds derived from carotenoids. Ethyl hex-(2E)-enoate and dihydroactinidiolide are exclusively present in the green teas derived from coarse leaves.
In general, coarse green teas irrespective of the method of processing contained more number of the volatile constituents, whereas the normal green teas irrespective of the method of processing contained less number of volatile constituents eluting before linalool. This can be attributed to the normal leaf quality, which contributes less volatiles from the group of constituents (Gr. I) which are undesirable, which is the prevalent practice in the industry as well. It is also evident from the results that normal as well as a commercial sample of green tea contained almost half the number of identified volatile constituents in the present investigation as compared to the coarse green teas contained. Dihydroactinidolide and ethyl hexenoate were found to be important markers and both were present in coarse green teas, whereas both were not found in the normal green teas including the commercial one. It can be concluded that the commercial green tea (Nilgiris green tea) is also prepared from the normal tea leaves. This can be very well used in spotting the normal / coarse green tea or the admixture of the coarse green tea leaves with the normal green tea leaves. Other important marker volatiles found were the both heptadienals [(E,Z)-2, 4 /
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(E,E)-2,4]. Coarse green tea contained both the heptadienals, whereas normal green teas did not contain any of the identified heptadienals in the present investigation. cis-3-hexenyl-n-hexanoate, ∝-ionone, cis-geranylacetone and β-ionone-5,6-epoxide were not found in a normal green tea. This can be attributed to the method of processing (CFD) and higher temperature (110°C) used.
Green tea extract
The extraction of green tea samples at lab scale, using different solvents (viz., Ethyl acetate, acetone, ethyl alcohol, methyl alcohol and their aqueous mixtures) was carried out.
The radical scavenging activity (RSA) of these extractives at 50 and 100 ppm concentrations were evaluated using the DPPH model system. The order of activity and extractability are as follows: Methanol > Ethanol> Acetone > Ethyl acetate The aqueous alcoholic mixtures showed higher activity and polyphenol extractability than the respective single solvents.
It was found that the yields of the extractives from green teas of coarse leaves are relatively low on the expected lines and the radical scavenging activities of the extractives of green teas from coarse leaves are marginally low at different concentrations. This observation indicated that the green teas from coarse leaves could be used for the preparation of radical scavenging conserves, by separating / enriching the active components using suitable technique.
Fractionation of the green tea extract
The extractives were subjected to liquid-liquid extraction using water and low molecular weight ester to fractionate the catechins into the solvent fraction. These extracts were analyzed for total polyphenol content and evaluated for radical scavenging activity. The polyphenol content of the solvent extracts found to be 30±2.3% as gallic acid equivalents for coarse leaves, while, polyphenol content of the solvent extract of normal leaves is found to be 31±2.4% as gallic acid equivalents. The total polyphenol content in the aqueous portion of these extracts is 23±2.1% as gallic acid equivalents for normal leaves, while that for coarse leaves extracts is found to be 18±3.0% as gallic acid equivalents. The
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yields of the solvent extracts are found to be 15±0.8% for coarse leaves and for normal leaves the yield of solvent extract is found to be 17±0.8%. The yield of the aqueous extract is 17±0.9 % for coarse leaves and for normal leaves the yield of solvent extract is found to be 19 ±1.0 %. However, the radical scavenging activity of the solvent extracts from both normal and coarse leaves is found to be same (92±1% at 15 ppm). The RSA of the aqueous extracts is found to be lower. Hence, it may be concluded that the solvent used separated the compounds responsible for the radical scavenging activity.
The data obtained reveal that the green tea extracts / conserve is free radical inhibitor and primary antioxidant that react with DPPH radical, which may be attributed to its hydrogen donating ability.
HPLC profiling of green tea extractives, chemical composition and quantification
The total catechin content in the green tea extract based on the comparison of peak areas of each peak with that of authentic samples and from calibration curves was found to be in the range of 20–30 %. After fractionation the solvent extract is enriched with catechin and the total catechin content is found to be in the range of 55-85 %, while the HPLC profile of aqueous extracts showed only the presence of gallic acid and caffeine.
Extracts from unused fresh green tea leaves have the potential for large-scale application as natural antioxidants. Extracts of the green tea are becoming increasingly important as functional ingredients in the diet and are being added to a range of foods and beverages.
Improved method for the active conserve
To minimize the processing cost and to control the epimerisation of catechins during processing, alternate methods were explored. Green tea sample from fresh batch was subjected to aqueous alcoholic extraction. The extract was concentrated to remove the alcohol to the extent possible. The
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obtained miscella was cooled to 10oC and kept over night at that temperature. The separated solids were filtered and dissolved in low molecular weight ester and the filtrate was also treated with the same ester. Solvent
Rapid refolding studies on the chaperone-like α-crystallin effect of α-crystallin on refolding of β- and γ-crystallins
No full textα-Crystallin, a multimeric protein present in the eye lens, is shown to have chaperone-like activity in preventing thermally induced aggregation of enzymes and other crystallins. We have studied the rapid refolding of α-crystallin, and compared it with other calf eye lens proteins, namely β- and γ-crystallins. α-Crystallin forms a clear solution upon rapid refolding from 8 M urea. The refolded α-crystallin has native-like secondary, tertiary, and quaternary structures as revealed by circular dichroism and fluorescence characteristics as well as gel filtration and sedimentation velocity measurements. On rapid refolding, β- and γ-crystallins aggregate and form turbid solutions. The presence of α-crystallin in the refolding buffer marginally increases the recovery of β- and γ-crystallins in the soluble form. However, unfolding of these crystallins together with α-crystallin using 8 M urea and subsequent refolding significantly increases the recovery of these proteins in the soluble form. These results indicate that an intermediate of α-crystallin formed during refolding is more effective in preventing the aggregation of β- and γ-crystallins. This supports our earlier hypothesis (Raman, B., and Rao, C. M.(1994) J. Biol. Chem. 269, 27264-27268) that the chaperone-like activity of α-crystallin is more pronounced in its structurally perturbed state
HSP90 modulates actin dynamics: Inhibition of HSP90 leads to decreased cell motility and impairs invasion
No full textAbstractHSP90, a major molecular chaperone, plays an essential role in the maintenance of several signaling molecules. Inhibition of HSP90 by inhibitors such as 17-allylamino-demethoxy-geldanamycin (17AAG) is known to induce apoptosis in various cancer cells by decreasing the activation or expression of pro-survival molecules such as protein kinase B (Akt). While we did not observe either decrease in expression or activation of pro-survival signaling molecules in human breast cancer cells upon inhibiting HSP90 with 17AAG, we did observe a decrease in cell motility of transformed cells, and cell motility and invasion of cancer cells. We found a significant decrease in the number of filopodia and lamellipodia, and in the F-actin bundles upon HSP90 inhibition. Our results show no change in the active forms or total levels of FAK and Pax, or in the activation of Rac-1 and Cdc-42; however increased levels of HSP90, HSP90α and HSP70 were observed upon HSP90 inhibition. Co-immuno-precipitation of HSP90 reveals interaction of HSP90 with G-actin, which increases upon HSP90 inhibition. FRET results show a significant decrease in interaction between actin monomers, leading to decreased actin polymerization upon HSP90 inhibition. We observed a decrease in the invasion of human breast cancer cells in the matrigel assay upon HSP90 inhibition. Over-expression of αB-crystallin, known to be involved in actin dynamics, did not abrogate the effect of HSP90 inhibition. Our work provides the molecular mechanism by which HSP90 inhibition delays cell migration and should be useful in developing cancer treatment strategies with known anti-cancer drugs such as cisplatin in combination with HSP90 inhibitors
Application of photoacoustics to biology: some specific systems and methods
No full text A recent review of applications of photoacoustic spectroscopy to biological systems is presented. Examples of chromophore studies by photoacoustic spectroscopy show that a good correlation is possible between their presence or interactions and the photoacoustic spectra. Emphasis is placed on new interpretations of the photoacoustic signal as well as new methods such as depth profiling, the mirage effect, and Fourier-transform photoacoustic spectroscopy. </jats:p
Temperature dependent chaperone-like activity of alpha-crystallin
No full textAbstractAlpha-crystallin, a multimeric protein present in the eye lens, is known to have chaperone-like activity in preventing the aggregation of enzymes and other crystallins. We have studied the chaperone-like activity of this protein towards the aggregation of insulin B chain, induced by reducing the interchain disulphide bond with dithiothreitol. At room temperature, there is no detectable protection (at a 1:1 (w/w) ratio of insulin: α-crystallin) against the aggregation of insulin B chain by α-crystallin, whereas it completely prevents this aggregation at 40°C. We have monitored the temperature dependence of the protection of aggregation by α-crystallin; the protection increases sharply above 30°C and reaches almost 100% by 41°C. Probing the hydrophobic surfaces of α-crystallin with the hydrophobic fluorphore 8-anilino-1 naphthalene sulfonate suggests that the hydrophobic surfaces of α-crystallin are exposed to a greater extent above 30°C. A complete prevention of the aggregation is achieved at 27.6°C by increasing the concentration of α-crystallin by more than 8 fold. Similar temperature dependent chaperone-like activity of α-crystallin is observed towards the aggregation of zetacrystallin, an enzyme crystallin from guinea pig. We have earlier shown that α-crystallin exposes hydrophobic surface(s) at temperatures above 30°C. These results support our earlier hypothesis [Raman, B. and Rao, Ch.M. (1994) J. Biol. Chem. 269, 27264–27268] that the chaperone-like activity of α-crystallin is more pronounced in its structurally perturbed state
Synchronous scan fluorescence spectroscopy of proteins and human eye lenses
No full textScanning both the excitation and emission monochromators synchronously while recording the fluorescence spectrum results in a considerable decrease in the apparent band width and shift in the peak position. We demonstrate the potential of this approach in the studies on proteins and their interactions as well as fluorophores in condensed media. We have chosen crystallins, eye lens proteins and human lenses. Synchronous scan spectra of α-, β- and γ-crystallins are clearly distinguishable and appear to provide specific signatures. The spectrum of the mixed solution could be simulated by the linear combination of components indicating that these proteins might not have any specific interaction in the dilute solutions. Synchronous spectra of the human lenses, both normal and cataractous, show several distinguishable features
Ubiquitin–proteasome-mediated degradation and synthesis of MyoD is modulated by αB-crystallin, a small heat shock protein, during muscle differentiation
No full textAbstractαB-crystallin, a small heat shock protein, plays an important role in muscle homeostasis. It gets up-regulated during muscle differentiation and mice lacking αB-crystallin die prematurely with extensive muscle wastage. We have examined the role of αB-crystallin in muscle development using C2C12 myoblasts as a model system. Over-expression of αB-crystallin delays the muscle differentiation program significantly. C2C12 myoblasts over-expressing αB-crystallin (CRYAB-C2C12) display defect in cell-cycle exit upon induction of differentiation. During differentiation, CRYAB-C2C12 cells exhibit sustained level of cyclin D1 and delay in p21 and myogenin expression as compared to C2C12 cells. We find less accumulation of MyoD in CRYAB-C2C12 cells than in C2C12 cells. In vivo protein stability studies reveal faster ubiquitin–proteasome-mediated MyoD degradation in CRYAB-C2C12 cells (t1/2=1.42 h) than in C2C12 cells (t1/2=2.37 h). Immuno-precipitation experiments showed that MyoD gets ubiquitinated at earlier time points in CRYAB-C2C12 cells than in C2C12 cells. Our data reveal alterations in the synthesis and degradation of MyoD in CRYAB-C2C12 cells. The level of αB-crystallin as well as its Ser-59 phosphorylated form increases with increasing time of differentiation. Our studies show, inter alia, that αB-crystallin modulates myogenesis by altering MyoD level and provide an interesting insight in its role in myogenesis
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