31 research outputs found
Analysis of the contribution of the p-acidity of the s-tetrazine ring in the crystal packing of coordination polymers
No full textReaction of manganese(II) with the electron-deficient ligand 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine (pbptz) leads to distinct coordination networks whose topologies are influenced by the nature of the anions used.
As anticipated, the linear ditopic ligand pbptz is involved in various types of supramolecular-p interactions, i.e.p...p, lone pair...p and C–H...p interactions, which clearly play a role in the formation of the different solid-state architectures obtained, as shown by DFT calculations
Neuronal adaptive responses to oxygen deprivation: alterations In glutamate receptor trafficking and mitochondrial dynamics
No full textAdaptability to changing environmental oxygen levels is important for the survival of aerobic organisms. Neurons in particular are vulnerable to oxygen deprivation (hypoxia), and hypoxia-induced degeneration is a hallmark of ischemic stroke, a leading cause of morbidity and disability. Ischemic stroke damages neurons through a combination of hypoxia-induced neuronal membrane depolarization, excess glutamate receptor activation, altered intracellular calcium homeostasis, and mitochondrial dysfunction. Neurons from different species or even from different brain regions of the same species have varying tolerances to oxygen deprivation, yet little is known about how neurons adapt to the stress of oxygen deprivation. Examining the causality of this differential resistance is particularly challenging in mammalian neurons given their inherent sensitivity to this stress. The soil nematode C. elegans serves as a hypoxia-adaptable model organism that can be used to examine how neurons handle oxygen deprivation. In the
dissertation work presented here, I have employed C. elegans to study the hypoxic regulation of two key cell biological components important for the progression of hypoxia–induced neuronal death: glutamate receptors and
mitochondria. In these studies, I report our identification of a novel variant of the hypoxia response pathway dedicated to the modulation of C. elegans glutamate receptor trafficking. In addition, I report that the dynamics of mitochondrial fission
and fusion are altered in response to oxygen deprivation in C. elegans neurons. I also present data suggesting that the canonical hypoxia response pathway regulates this dynamic response. These alterations in glutamate receptor trafficking and mitochondrial dynamics are accompanied by behavioral changes and possibly promote survival in response to oxygen deprivation. My findings indicate that neurons protect themselves by executing a complex and multilayered homeostatic response to reduced oxygen availability that
incorporates both transcriptional and posttranslational mechanisms.Ph. D.Includes bibliographical referencesby Piya Ghos
A mixed-valence Mn<sub>6</sub> cluster exhibiting self-assembled vesicular structure and catecholase-like activity in solution state
No full textThe reaction of Mn(OBz)2•4H2O (OBz = benzoate) with hmt (hmt = hexamethylenetetramine) in CH3CN affords a mixed-valence hexanuclear complex [MnIII2MnII4O2 (hmt)4(OBz)10] (1). The complex has been characterized in solid state by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. X-ray crystal structure reveals that 1 consists of a [MnIII2MnII4O2] core, co-ordinated to ten bridging benzoates (six syn,-syn-η1:η1:μ 2, four η1:η2:μ3) and four terminal hmt groups. In solution state (acetonitrile solvent) 1 spontaneously forms self-assembled vesicular structure with diameter in the range of 100–150 nm. The morphology in solution state has been studied through various microscopic techniques like SEM, TEM, AFM etc. These self-assembled vesicular structures can encapsulate organic dye molecules, which have been confirmed by confocal microscopic imaging. Complex 1 also exhibits substantial catecholase-like activity with 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate in acetonitrile solvent; the Kcat value is determined to be 2337.9 h−1
miR778 mediates gene expression, histone modification, and DNA methylation during cyst nematode parasitism
No full textDespite the known critical regulatory functions of microRNAs, histone modifications, and DNA methylation in reprograming plant epigenomes in response to pathogen infection, the molecular mechanisms underlying the tight coordination of these components remain poorly understood. Here, we show how Arabidopsis (Arabidopsis thaliana) miR778 coordinately modulates the root transcriptome, histone methylation, and DNA methylation via post-transcriptional regulation of the H3K9 methyltransferases SU(var)3-9 homologue 5 (SUVH5) and SUVH6 upon infection by the beet cyst nematode Heterodera schachtii. miR778 post-transcriptionally silences SUVH5 and SUVH6 upon nematode infection. Manipulation of the expression of miR778 and its two target genes significantly altered plant susceptibility to H. schachtii. RNA-seq analysis revealed a key role of SUVH5 and SUVH6 in reprograming the transcriptome of Arabidopsis roots upon H. schachtii infection. In addition, ChIP-seq analysis established SUVH5 and SUVH6 as the main enzymes mediating H3K9me2 deposition in Arabidopsis roots in response to nematode infection. ChIP-seq analysis also showed that these methyltransferases possess distinct DNA binding preferences in that they are targeting transposable elements under non-infected conditions and protein-coding genes in infected plants. Further analyses indicated that H3K9me2 deposition directed by SUVH5 and SUVH6 contributes to gene expression changes both in roots and in nematode feeding sites and preferentially associates with CG DNA methylation. Together, our results uncovered multi-layered epigenetic regulatory mechanisms coordinated by miR778 during Arabidopsis–H. schachtii interactions.This is a pre-copyedited, author-produced version of an article accepted for publication in Plant Physiology following peer review. The version of record: Bennett, Morgan, Sarbottam Piya, Thomas J. Baum, and Tarek Hewezi. "miR778 mediates gene expression, histone modification, and DNA methylation during cyst nematode parasitism." Plant Physiology (2022) is available online at DOI: 10.1093/plphys/kiac228. Copyright 2022 American Society of Plant Biologists. Posted with permission
Tuning of exchange coupling by the Mn–O distance and phenoxido bridging angle: an experimental and theoretical study of the family of Mn(iii) dimers with salen type ligands
No full textThree new Mn(III) complexes [Mn2L2(ClO4)2] (1), [Mn2L2(NCS)2] (2) and [Mn2L2N(CN)2]ClO4•CH3CN (3) have been synthesized from the Schiff base ligand H2L (where H2L = N,N′-bis(2-hydroxypropiophenone)-1,2- ethanediamine) and various anionic coligands e.g. perchlorate, thiocyanate and dicyanamide. X-ray crystal structure analysis reveals that 1 and 2 are dinuclear complexes, joined together by Mn⋯O (phenoxido) interactions. Whereas 3 consists of an alternating phenoxido and μ1,5 dicyanamido bridge, resulting in a 1D chain. In 1 and 2 ferromagnetic coupling exists between the Mn(III) centres within the dimer but 3 possesses antiferromagnetic interaction. This difference in magnetic exchange interactions has been rationalized on the basis of structural parameters like longer bridging Mn–O distance and Mn–O–Mn angle in these complexes with the help of DFT calculations
The relationship between obstructive sleep apnea and intra-epidermal nerve fiber density, PARP activation and foot ulceration in patients with type 2 diabetes.
No full textAuthor(s) Pre or Post Print Version onlyBACKGROUND: Obstructive sleep apnea (OSA) is associated with increased nitrosative stress, endothelial dysfunction, and peripheral neuropathy in patients with type 2 diabetes. We hypothesized that OSA is associated with Poly ADP ribose polymerase (PARP) activation, lower intra-epidermal nerve fiber density (IENFD), and diabetic foot ulceration (DFU). METHODS: A cross-sectional study of adults with type 2 diabetes recruited from a secondary care hospital in the UK. OSA was assessed by multi-channel home-based cardio-respiratory device (Alice PDX, Philips Respironics). DPN was assessed using the Michigan Neuropathy Screening Instrument (MNSI). IENFD and % PAR stained nuclei were assessed using immunohistochemistry staining on skin biopsies. DFU was assessed based on MNSI. RESULTS: Skin biopsies and DFU data were available from 52 and 234 patients respectively. OSA was associated with lower IENFD (12.75±1.93 vs. 10.55±1.62 vs. 9.42±1.16 fibers/mm of epidermis for no OSA, mild OSA and moderate to severe OSA respectively, p<0.001). Following adjustment, mild (B= 2.19, p=0.002) and moderate to severe OSA (B=-3.45, p<0.001) were independently associated with IENFD. The apnea hypopnea index (AHI) was associated with IENFD following adjustment (B=-2.45, p<0.001). AHI was associated with percentage of PAR stained nuclei following adjustment (B=13.67, p=0.025). DFU prevalence was greater in patients with OSA (7.1% vs. 28.1% vs. 26.2% for patients with no OSA, mild OSA and moderate to severe OSA respectively, p=0.001). Following adjustment, OSA was associated with DFU (OR 3.34, 95% CI 1.19-9.38, p=0.022). CONCLUSIONS: OSA is associated with lower IENFD, PARP activation and DFU in patients with type 2 diabetes. Our findings suggest that OSA is associated with small fiber neuropathy. PARP activation is a potential mechanisms linking OSA to DPN and endothelial dysfunction in patients with type 2 diabetes. Whether OSA treatment will have a favorable impact on these parameters and DFU requires interventional studies
Complexes: Experimental Observations and Theoretical Rationalization
No full textThree new trinuclear heterometallic NiII–MnII complexes have been synthesized using a [NiL] metalloligand, where H2L = N,N′-bis(salicylidene)-1,3-propanediamine. The complexes [(NiL)2Mn(OCnn)2(CH3OH) 2]•CH3OH (1), [(NiL) 2Mn(OPh)2(CH3OH) 2][(NiL)2Mn(OPh) 2]•H2O (2), and [(NiL)2Mn(OSal) 2(CH3OH)2]•2[NiL] (3) (where OCnn = cinnamate, OPh = phenylacetate, OSal = salicylate) have been structurally characterized. In all three complexes, in addition to the double phenoxido bridge, the two terminal NiII atoms are linked to the central MnII by means of a syn-syn bridging carboxylate, giving rise to a linear structure. Complexes 1 and 2 with Ni–O–Mn angles of 97.24 and 96.43°, respectively, exhibit ferromagnetic interactions (JNi–Mn = +1.38 and +0.50 cm–1, respectively), whereas 3 is antiferromagnetic (JNi–Mn = −0.24 cm–1), having an Ni–O–Mn angle of 98.51°. DFT calculations indicate that there is a clear magneto-structural correlation between the Ni–O–Mn angle and JNi–Mn values, which is in agreement with the experimental results
Analyses of supramolecular interactions present in a coordination polymer of Mn(II) with 2-picolinate and 4,4′-Azobis(pyridine)
No full textA new 2D coordination polymer [MnII(pic)(4,4′ -azpy)(H2O)]ClO4•EtOH (pic = 2-picolinate) has been synthesized where each of the octahedral Mn(II) center is connected by trans coordinating 4,4′-azpy and syn-anti bridging picolinate, resulting in a sheet like structure. Density Functional Theory (DFT) calculations, at the BLYP-D3/def2-TZVPD level of theory, are performed to explore the interplay of various supramolecular interactions present within the coordination polymer
Analyses of supramolecular interactions present in a coordination polymer of Mn(II) with 2-picolinate and 4,4′-Azobis(pyridine)
No full text[eng]A new 2D coordination polymer [MnII(pic)(4,4′ -azpy)(H2O)]ClO4·EtOH (pic = 2-picolinate) has been synthesized where each of the octahedral Mn(II) center is connected by trans coordinating 4,4′-azpy and syn-anti bridging picolinate, resulting in a sheet like structure. Density functional theory (DFT) calculations, at the BLYP-D3/def2-TZVPD level of theory, are performed to explore the interplay of various supramolecular interactions present within the coordination polymer
Trinuclear heterometallic Cu<sup>II</sup>–Mn<sup>II</sup> complexes of a salen type Schiff base ligand: anion dependent variation of phenoxido bridging angles and magnetic coupling
No full textFive new trinuclear heterometallic CuII–MnII complexes [(CuL) 2Mn(O2CPh)2] (1), [(CuL) 2Mn(N3)2] (2), [(CuL) 2Mn(NCO)2] (3), [(CuL) 2Mn(NO3)2] (4) and [(CuL) 2Mn(Sal) 2]•CH2Cl2 (5) have been synthesized with the di-Schiff base ligand H2L (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine and Sal = salicylate). These complexes with different anionic co-ligands have been synthesized to attain a large variation in phenoxido bridging angles and to investigate its consequence on magnetic properties. Single crystal X-ray diffraction analyses reveal that complexes 1, 2, 4 and 5 are linear, whereas 3 has an angular geometry. Variable temperature magnetic susceptibility measurements suggest that all five complexes possess an overall antiferromagnetic interaction between CuII and MnII ions, which results in a final ferrimagnetic ground state with spin 3/2 in the CuII–MnII–CuII trinuclear structure. The weakest antiferromagnetic interaction (JCu–Mn = −7.0 cm−1) is observed for 2 having the lowest value of the Cu–O–Mn angle (92.0°), while the strongest antiferromagnetic interaction (JCu–Mn = −26.5 cm−1) is observed for 3 having the largest Cu–O–Mn angle (101.4°). Complexes 1, 4 and 5 show average Cu–O–Mn angles of 98.2°, 97.6° and 97.7°, respectively, that lead to intermediate antiferromagnetic interactions (JCu–Mn = −9.6, −9.7, −9.3 cm−1 respectively)
