STRUCTURAL AND FUNCTIONAL STUDIES ON GABAA RECEPTOR SUBTYPES: A COMPUTATIONAL PATHWAY FOR DESIGNING NOVEL NON-SEDATIVE MODULATORS

In this stressful era, maintaining the proper balance of neuronal excitation and inhibition remains the central demand of human brain. To harmonize the optimal brain functioning, γ-Amino Butyric Acid type A Receptors (GABAA-Rs) play a vital role by mediating the fast inhibitory neurotransmissions. These GABA-gated chloride ion channels maintain the delicate balance between neuronal excitation and inhibition. The formation of GABAA-R uses repertoire of 19 different subunit subtypes α1-6, β1-3, γ1-3, δ, ε, π, θ and ρ1-3, out of which two α1, two β2 and one γ2 form the most abundant native GABAA-R structure. In the absence of heteropentameric human GABAA-R structure the structural biology remains yet to be fully explored. Manipulation of GABAergic transmission is aimed to provide the benefits in the treatment of a host of neurological and psychiatric disorders. We utilised the existing experimental data and carried out a computational study to obtain the structural details of different GABAA-Rs. This computational pathway sequentially proceeds for : i) obtaining the different GABAA-R states and subtypes; ii) understanding the logic of their existence and correlating structure-function details for each of them; iii) unravelling the complete journey of molecular events that fine tune the state dependent channel transitions in normal conditions including ligand unoccupied closed, open, uncapped receptive states and GABA occupied singly and doubly bound states; iv) understanding the nature of cross-talk between two orthosteric sites and third allosteric BZD-site when we brought it into consideration; v) identifying a set of governing rules/markers forming the structural basis of selective modulation for BZD-site agonists at α1- and α2-GABAA-R subtypes. Accordingly, to fulfil the deliberate demand of clinically efficacious α2-selective non-sedative modulator/s the underlying logic is systematically demarcated under single platform. The crux from the early stage modulatory pathways of subtype selective actions provides newer avenues to guide the designing of novel modulator/s having desired pharmacological endpoints in diseased states. Overall, this channelled study is bound to track the structure-function-novel drug designing, based on the understanding of GABAA-R modulatory pathways

An observational study of adverse drug reactions reported in a rural tertiary care hospital

Background: Adverse drug reactions (ADRs) are noxious and unintended effects of a drug that occurs at doses normally used in humans. ADRs may also result in diminished quality of life, increased physician visits, hospitalizations, and even death. The objectives of this study are to analyze and assess the causality and severity of reported ADRs.Methods: A cross sectional study of ADRs reported to Pharmacovigilance cell of MNR Medical College and Hospital Sangareddy in a year. The details of the various ADRs were statistically analyzed to find out pattern of ADRs. The WHO-UMC causality category and Hartwig-Seigel Scale were used to assess causality and severity of ADRs respectively.Results: The study shows, out of 60 suspected ADRs, the majority of ADRs were adults (68.3%) and out of whom 56% were females. According to the WHO-UMC Causality categories, 43.3% of the ADRs were categorized under Probable/likely, followed by possible (35%). The Hartwig-Siegel severity assessment scale shows that the majority (90%) of suspected ADRs were of mild category.Conclusions: The pattern of ADRs reported in our study is comparable to other studies. The commonest organ system affected was gastrointestinal tract, nervous and cutaneous system. Antimicrobial agents were causing maximum ADRs and medicine and allied departments have more number of ADRs. This study provides a valuable database for ADRs due to all commonly used drugs at hospitals and also helps in creating awareness regarding safe & judicious use of drugs to prevent ADRs

Fish immunology 

If a piece of life tissue of a person is grafted to another person, after a short period the transplanted tissue will be disintegrated and disappear. Also in most infectious diseases , the victim will be resistant against the malady after recovery. Such body responses are are called Immunological reactions and the study of these reactions, mechanisms involved and related consequences is known as Irnmunology. Of the most important applications of Immunology are disease prophilaxy (through vaccination), diagnosis and treatment.....

Capturing state-dependent dynamic events of GABAA-receptors: a microscopic look into the structural and functional insights

The γ-amino butyric acid type A receptors (GABAA-Rs) are the key players in the mammalian brain that meditate fast inhibitory neurotransmission events. The structural integrity of these ligand-gated ion channel controls chloride ion permeability, which in turn monitors important pharmacological functions. Despite ample studies on GABAA-Rs, there was a need for a study on full-length receptor structures, devoted to track structure–function correlations based on their dynamic behavior consideration. We have employed molecular dynamics simulations accompanied by other biophysical methods to shed light on sequential and unaddressed questions like How GABAA-R structure facilitates the entry of GABA molecules at its two orthosteric binding sites? After entry, what structural features and changes monitor site-wise GABA binding differences? In the same context, what are the roles and responsibilities of loops such as C and F? On physiologically relevant time scales, how open to close state transition occurs? How salt bridges such as E155-R207 and E153-R207 maintain statedependent C-loop structures? In an attempt, our simulation study unravels the complete course of GABA binding-unbinding pathway. This provides us with the relevant understanding of state-dependent dynamic events of GABAA-Rs

Binding of the Iminium and Alkanolamine Forms of Sanguinarine to Lysozyme: Spectroscopic Analysis, Thermodynamics, and Molecular Modeling Studies

Sanguinarine (SGR) exists in charged iminium (SGRI) and neutral alkanolamine (SGRA) forms. The binding of these two forms to the protein lysozyme (Lyz) was investigated by fluorescence, UV−vis absorbance and circular dichroism spectroscopy, and in silico molecular docking approaches. Binding thermodynamics were studied by microcalorimetry. Both forms of sanguinarine quenched the intrinsic fluorescence of Lyz, but the quenching efficiencies varied on the basis of binding that was derived after correction for an inner-filter effect. The equilibrium binding constants at 25 ± 1.0 °C for the iminium and alkanolamine forms were 1.17 × 105 and 3.32 × 105 M−1, respectively, with approximately one binding site for both forms of the protein. Conformational changes of the protein in the presence of SGR were confirmed by absorbance, circular dichroism, threedimensional fluorescence, and synchronous fluorescence spectroscopy. Microcalorimetry data revealed that SGRI binding is endothermic and predominantly involves electrostatic and hydrophobic interactions, whereas SGRA binding is exothermic and dominated by hydrogen-bonding interactions. The molecular distances (r) of 3.27 and 3.04 nm between the donor (Lyz) and the SGRI and SGRA acceptors, respectively, were calculated according to Förster’s theory. These data suggested that both forms were bound near the Trp-62/63 residues of Lyz. Stronger binding of SGRA than SGRI was apparent from the results of both structural and thermodynamic experiments. Molecular docking studies revealed that the putative binding site for the SGR analogues resides at the catalytic site. The docking results are in accordance with the spectroscopic and thermodynamic data, further validating the stronger binding of SGRA over SGRI to Lyz. The binding site is situated near a deep crevice on the protein surface and is close to several crucial amino acid residues, including Asp-52, Glu-35, Trp-62, and Trp-63. This study advances our knowledge of the structural nature and thermodynamic aspects of binding between the putative anticancer alkaloid sanguinarine and lysozyme

Chelerythrine–lysozyme interaction: spectroscopic studies, thermodynamics and molecular modeling exploration

The binding of the iminium and alkanolamine forms of chelerythrine to lysozyme (Lyz) was investigated by spectroscopy and docking studies. The thermodynamics of the binding was studied by calorimetry. Spectroscopic evidence suggested that Trp-62 and Trp-63 in the b-domain of the protein are closer to the binding site; moreover, the binding site was at a distance of 2.27 and 2.00 nm from the iminium and alkanolamine forms, respectively, according to the Forster theory of non-radiation energy transfer. The equilibrium binding constants for the iminium and alkanolamine forms at 298 K were evaluated to be 1.29 � 105 and 7.79 � 105 M�1, respectively. The binding resulted in an alteration of the secondary structure of the protein with a distinct reduction of the helical organization. The binding of iminium was endothermic, involving electrostatic and hydrophobic interactions, while that of alkanolamine form was exothermic and dominated by hydrogen bonding interactions. Docking studies provided the atomistic details pertaining to the binding of both forms of chelerythrine and supported the higher binding in favour of the alkanolamine over the iminium. Furthermore, molecular dynamics study provided accurate insights regarding the binding of both chelerythrine forms in accordance with the experimental results obtained. Chelerythrine binding pocket involves the catalytic region and aggregation prone K-peptide region, which are sandwiched between one another. Overall, these results suggest that both the forms of the alkaloid bind to the protein but the neutral form has higher affinity than the cationic form