Lectin binding to complex carbohydrate at the interface: a study by resonance energy transfer.

The binding affinity of the oligosaccharide moiety of a neutral glycosphingolipid, asialoGM1, towards Ricinus communis agglutinin (RCAI) was determined for the first time by fluorescence resonance energy transfer (RET). The asialoGM1 was incorporated into a phospholipid (DMPC) vesicle doped with dansylated DPPE and then titrated with an increasing amount of the galactose specific RCAI. The efficiency of RET was determined by a saturable increase in the quenching of 'donor' fluorescence, i.e. the 'trp' residue of RCAI, due to the energy transfer from the 'acceptor' dansyl group on the surface of the vesicle. The apparent binding constant was found to be in the range of 10(5)-10(6) M-1 at 27 degrees C.     

CCR5 Revisited: How Mechanisms of HIV Entry Govern AIDS Pathogenesis

The chemokine receptor CCR5 has been the focus of intensive studies since its role as a coreceptor for HIV entry was discovered in 1996. These studies lead to the development of small molecular drugs targeting CCR5, with maraviroc becoming in 2007 the first clinically approved chemokine receptor inhibitor. More recently, the apparent HIV cure in a patient transplanted with hematopoietic stem cells devoid of functional CCR5 rekindled the interest for inactivating CCR5 through gene therapy and pharmacological approaches. Fundamental research on CCR5 has also been boosted by key advances in the field of G-protein coupled receptor research, with the realization that CCR5 adopts a variety of conformations, and that only a subset of these conformations may be targeted by chemokine ligands. In addition, recent genetic and pathogenesis studies have emphasized the central role of CCR5 expression levels in determining the risk of HIV and SIV acquisition and disease progression. In this article, we propose to review the key properties of CCR5 that account for its central role in HIV pathogenesis, with a focus on mechanisms that regulate CCR5 expression, conformation, and interaction with HIV envelope glycoproteins.     

RNAi-based transgene conferred extreme resistance to the geminivirus causing apical leaf curl disease in potato

Potato apical leaf curl disease is an emerging geminiviral disease in tropics and subtropics. It was reported for the first time in the year 1999 in northern plains of India but quickly spread to almost all potato growing regions of the country largely due to prevalence of warmer weather during early crop growth, thereby favoring whitefly vector. The problem of apical leaf curl disease in India became more severe due to lack of seed indexing for this virus in conventional seed production scheme. Although it accounts for major yield loss, there is no conventional source of resistance available in potato against Tomato Leaf Curl New Delhi Virus-Potato (ToLCNDV-Potato) that causes this disease in potato. In the present study, we have investigated the potential use of RNAi for obtaining resistance against this DNA virus in potato. The replication-associated protein gene (AC1) of the virus was used to obtain pathogen-derived resistance. The AC1 gene was PCR amplified from field-infected potato leaves, cloned and sequenced (JN393309). It showed 93% sequence similarity with the AC1 gene of Tomato Leaf Curl Virus-New Delhi (TOLCV-NDe; DQ169056) virus. Transgenic plants encoding the AC1 gene in three different orientations, viz. sense, antisense and hairpin loop, were raised. Transgenic lines when challenge inoculated with ToLCNDV-Potato showed different levels of resistance for all three constructs. Transgene integration and copy number in selected transgenic lines were determined by qPCR and further confirmed by Southern blot analysis. Though a reduction in viral titer was observed in transgenic lines encoding either antisense or hairpin loop constructs of AC1 gene, the latter transgenics showed most significant results as shown by reduction in the level of symptom expression in glasshouse screening as well as real-time data of in vivo virus concentration. In fact, we obtained a few totally asymptomatic transgenic lines with hairpin loop strategy.     

Boltzmann Entropy: Generalization and Applications

The object of the paper is to generalize Boltzmann entropy to takeaccount of the subjective nature of a system. The generalized entropyor relative entropy so obtained has been applied to an ecologicalsystem leading to some interesting new results in violation ofexisting physical laws. The entropy was further developed to derive ageneralized macroscopic measure of relative entropy which plays asignificant role in the study of stability and evolution ofecological and chemical reaction systems.     

Anion induced conformational preference of CαNN motif residues in functional proteins

Among different ligand binding motifs, anion binding C^αNN motif consisting of peptide backbone atoms of three consecutive residues are observed to be important for recognition of free anions, like sulphate or biphosphate and participate in different key functions. Here we study the interaction of sulphate and biphosphate with C^αNN motif present in different proteins. Instead of total protein, a peptide fragment has been studied keeping C^αNN motif flanked in between other residues. We use classical force field based molecular dynamics simulations to understand the stability of this motif. Our data indicate fluctuations in conformational preferences of the motif residues in absence of the anion. The anion gives stability to one of these conformations. However, the anion induced conformational preferences are highly sequence dependent and specific to the type of anion. In particular, the polar residues are more favourable compared to the other residues for recognising the anion.     

Quinone and oxyradical scavenging properties of N-acetylcysteine prevent dopamine mediated inhibition of Na+, K+-ATPase and mitochondrial electron transport chain activity in rat brain: implications in the neuroprotective therapy of Parkinson's disease

Dopamine oxidation products such as H2O2 and reactive quinones have been held responsible for various toxic actions of dopamine, which have implications in the aetiopathogenesis of Parkinson's disease. This study has shown that N-acetylcysteine (0.25-1 mm) is a potent scavenger of both H2O2 and toxic quinones derived from dopamine and it further prevents dopamine mediated inhibition of Na+,K+-ATPase activity and mitochondrial respiratory chain function. The quinone scavenging ability of N-acetylcysteine is presumably related to its protective effect against dopamine mediated inhibition of mitochondrial respiratory chain activity. However, both H2O2 scavenging and quinone scavenging properties of N-acetylcysteine probably account for its protective effect against Na+,K+-ATPase inhibition induced by dopamine. The results have important implications in the neuroprotective therapy of sporadic Parkinson's disease since inactivation of mitochondrial respiratory activity and Na+,K+-ATPase may trigger intracellular damage pathways leading to the death of nigral dopaminergic neurons.