G-SERF Editing in Two-Dimensional Pure-Shift Total Correlation Spectroscopy: Scalar Coupling Measurements for a Group of Spins in Organic Molecules.

A novel G-SERF-PSYCHE-TOCSY (gradient encoded selective refocusing in pure shift yielded by chirp excitation version of total correlation spectroscopy) NMR pulse scheme has been proposed, which produces TOCSY chemical shift correlations, on one hand, and scalar coupling values for the spins scalarly coupled to irradiated resonances, by showing them as doublets along the indirect dimension, on the other. Therefore, recording such an experiment, for a group of spins with overlapping chemical shifts, in organic molecules can adequately provide scalar coupling information in a G-SERF manner along the indirect dimensions, and they can be assigned to particular spin pairs. Such COSY chemical shift correlations (which appear as doublets for the scalarly coupled spins) can be readily discriminated from the TOCSY peaks (which do not show such splitting) in the G-SERF-PSYCHE-TOCSY spectrum.

Structure-aided drug development of potential neuraminidase inhibitors against pandemic H1N1 exploring alternate binding mechanism.

The rate of mutability of pathogenic H1N1 influenza virus is a threat. The emergence of drug resistance to the current competitive inhibitors of neuraminidase, such as oseltamivir and zanamivir, attributes to a need for an alternative approach. The design and synthesis of new analogues with alternate approach are particularly important to identify the potential neuraminidase inhibitors which may not only have better anti-influenza activity but also can withstand challenge of resistance. Five series of scaffolds, namely aurones (1a-1e), pyrimidine analogues (2a-2b), cinnamic acid analogues (3a-3k), chalcones (4a-4h) and cinnamic acid linkages (5a-5c), were designed based on virtual screening against pandemic H1N1 virus. Molecular modelling studies revealed that the designed analogues occupied 430-loop cavity of neuraminidase. Docking of sialic acid in the active site preoccupied with the docked analogues, i.e. in 430-loop cavity, resulted in displacement of sialic acid from its native pose in the catalytic cavity. The favourable analogues were synthesized and evaluated for the cytotoxicity and cytopathic effect inhibition by pandemic H1N1 virus. All the designed analogues resulting in displacement of sialic acid suggested alternate binding mechanism. Overall results indicated that aurones can be measured best among all as potential neuraminidase inhibitor against pandemic H1N1 virus.

Probing the Potential Role of Non-B DNA Structures at Yeast Meiosis-Specific DNA Double-Strand Breaks.

A plethora of evidence suggests that different types of DNA quadruplexes are widely present in the genome of all organisms. The existence of a growing number of proteins that selectively bind and/or process these structures underscores their biological relevance. Moreover, G-quadruplex DNA has been implicated in the alignment of four sister chromatids by forming parallel guanine quadruplexes during meiosis; however, the underlying mechanism is not well defined. Here we show that a G/C-rich motif associated with a meiosis-specific DNA double-strand break (DSB) in Saccharomyces cerevisiae folds into G-quadruplex, and the C-rich sequence complementary to the G-rich sequence forms an i-motif. The presence of G-quadruplex or i-motif structures upstream of the green fluorescent protein-coding sequence markedly reduces the levels of gfp mRNA expression in S. cerevisiae cells, with a concomitant decrease in green fluorescent protein abundance, and blocks primer extension by DNA polymerase, thereby demonstrating the functional significance of these structures. Surprisingly, although S. cerevisiae Hop1, a component of synaptonemal complex axial/lateral elements, exhibits strong affinity to G-quadruplex DNA, it displays a much weaker affinity for the i-motif structure. However, the Hop1 C-terminal but not the N-terminal domain possesses strong i-motif binding activity, implying that the C-terminal domain has a distinct substrate specificity. Additionally, we found that Hop1 promotes intermolecular pairing between G/C-rich DNA segments associated with a meiosis-specific DSB site. Our results support the idea that the G/C-rich motifs associated with meiosis-specific DSBs fold into intramolecular G-quadruplex and i-motif structures, both in vitro and in vivo, thus revealing an important link between non-B form DNA structures and Hop1 in meiotic chromosome synapsis and recombination.

Serum metabolomics of Indian women with polycystic ovary syndrome using 1H NMR coupled with a pattern recognition approach.

Polycystic ovary syndrome (PCOS) is one of the most commonly occurring metabolic and endocrinological disorders affecting women of reproductive age. Metabolomics is an emerging field that holds promise in understanding disease pathophysiology. Recently, a few metabolomics based studies have been attempted in PCOS patients; however, none of them have included patients from the Indian population. The main objective of this study was to investigate the serum metabolomic profile of Indian women with PCOS and compare them with controls. Proton nuclear magnetic resonance (1H NMR) was used to first identify the differentially expressed metabolites among women with PCOS from the Eastern region of India during the discovery phase and further validated in a separate cohort of PCOS and control subjects. Multivariate analysis of the binned spectra indicated 16 dysregulated bins in the sera of these women with PCOS. Out of these 16 bins, 13 identified bins corresponded to 12 metabolites including 8 amino acids and 4 energy metabolites. Amongst the amino acids, alanine, valine, leucine and threonine and amongst the energy metabolites, lactate and acetate were observed to be significantly up-regulated in women with PCOS when compared with controls. The remaining 4 amino acids, l-glutamine, proline, glutamate and histidine were down-regulated along with 2 energy metabolites: glucose and 3-hydroxybutyric acid. Our findings showed dysregulations in the expression of different metabolites in the serum of women with PCOS suggesting the involvement of multiple pathways including amino acid metabolism, carbohydrate/lipid metabolism, purine and pyrimidine metabolism and protein synthesis.

Repeated implantation failure versus repeated implantation success: discrimination at a metabolomic level.

STUDY QUESTION: Is there any difference at the serum metabolic level between women with recurrent implantation failure (RIF) and women with recurrent implantation success (RIS) when undergoing in vitro fertilization (IVF)? SUMMARY ANSWER: Eight metabolites, including valine, adipic acid, l-lysine, creatine, ornithine, glycerol, d-glucose and urea, were found to be significantly up-regulated in women with RIF when compared with women with RIS. WHAT IS KNOWN ALREADY: Despite transfer of three high-grade embryos per cycle, RIF following three or more consecutive IVF attempts occurs in a group of infertile women. Conversely, there is a group of women who undergo successful implantation each cycle, yet have a poor obstetric history. STUDY DESIGN, SIZE, DURATION: This study was conducted over a period of 10 years (January 2004-October 2014). Groups of 28 women with RIF (age ≤40 years and BMI ≤28) and 24 women with RIS (age and BMI matched) were selected from couples with primary infertility reporting at the Institute of Reproductive Medicine, Kolkata, India. Women recruited in the RIF group had history of implantation failure in at least three consecutive IVF attempts, in which three embryos of high-grade quality were transferred in each cycle. PARTICIPANTS/MATERIALS, SETTING, METHODS: Blood samples were collected from both the groups during the implantation window following overnight fasting for at least 10 h (7-10 days post ovulation). Samples were analyzed using a 700 MHz NMR spectrometer and acquired spectra were subjected to chemometric and statistical analysis. Serum levels of endothelial nitric oxide synthase (eNOS) were measured using an enzyme immunoassay technique. MAIN RESULTS AND THE ROLE OF CHANCE: Valine, adipic acid, l-lysine, creatine, ornithine, glycerol, d-glucose and urea were found to be significantly down-regulated in women with RIS when compared with those with RIF, with fold change values of 0.81, 0.82, 0.79, 0.80, 0.78, 0.68, 0.76 and 0.74, respectively. Further, serum eNOS was found to be significantly lower in women with RIF when compared with RIS (P < 0.05), indicating possible impairment in nitric oxide production. Metabolites, mostly related to energy metabolism, lipid metabolism and the arginine metabolic pathway were found to be considerably altered and are likely to be associated with the RIF phenomenon. However, the interplay between these molecules in RIF is complex and holds merit for further exploration. LIMITATIONS, REASONS FOR CAUTION: In-depth studies of the arginine metabolic pathway in endometrial tissues seem necessary to validate our findings. A limitation of the present study is that the metabolic level changes, eNOS and nitric oxide levels have not been investigated in the endometrial tissues of the two groups of women. It would be interesting to investigate whether there exists a direct link between metabolic dysregulation and genetic factors that affects implantation in RIF women. WIDER IMPLICATIONS OF THE FINDINGS: We speculate that tissue metabolomics can provide an improved understanding of the metabolic dysfunction associated with RIF. The identification of serum metabolic marker(s) in women with RIS may help with strategies of early therapeutic intervention, which may improve the chances of implantation significantly in women otherwise susceptible to IVF failure. STUDY FUNDING/COMPETING INTERESTS: One of the authors, S.R.C. acknowledges the Council of Scientific and Industrial Research (CSIR), Government of India [No: 9/81(1228)/14, EMR-I] for financial support.

Formation of a G-quadruplex at the BCL2 major breakpoint region of the t(14;18) translocation in follicular lymphoma.

The t(14;18) translocation in follicular lymphoma is one of the most common chromosomal translocations. Most breaks on chromosome 18 are located at the 3'-UTR of the BCL2 gene and are mainly clustered in the major breakpoint region (MBR). Recently, we found that the BCL2 MBR has a non-B DNA character in genomic DNA. Here, we show that single-stranded DNA modeled from the template strand of the BCL2 MBR, forms secondary structures that migrate faster on native PAGE in the presence of potassium, due to the formation of intramolecular G-quadruplexes. Circular dichroism shows evidence for a parallel orientation for G-quadruplex structures in the template strand of the BCL2 MBR. Mutagenesis and the DMS modification assay confirm the presence of three guanine tetrads in the structure. 1H nuclear magnetic resonance studies further confirm the formation of an intramolecular G-quadruplex and a representative model has been built based on all of the experimental evidence. We also provide data consistent with the possible formation of a G-quadruplex structure at the BCL2 MBR within mammalian cells. In summary, these important features could contribute to the single-stranded character at the BCL2 MBR, thereby contributing to chromosomal fragility.

Hierarchy in guanidine unfolding of DLC8 dimer: regulatory functional implications.

Folding-unfolding caused by environmental changes play crucial regulatory roles in protein functions. To gain an insight into these for DLC8, a cargo adaptor in dynein motor complex, we investigated here the unfolding of homodimeric DLC8 by GdnHCl, a standard unfolding agent. Fluorescence spectroscopy revealed a three-state unfolding transition with midpoints at 1.5 and 4.0 M GdnHCl. The HSQC spectrum at 1.5 M GdnHCl displayed peaks belonging to a folded monomer. NMR chemical shift perturbations, line broadening effects and (15)N relaxation measurements at low GdnHCl concentrations identified a hierarchy in the unfolding process, with the dimer interface--the cargo binding site--being the most susceptible followed by the helices in the interior. Similar observations were made earlier for small pH perturbations and thus the early unfolding events appear to be intrinsic to the protein. These, by virtue of their location, influence target binding efficacies and thus have important regulatory implications.