Temperature induced hyperchromism exhibited by Hoechst 33258: evidence of drug aggregation from UV-melting method

UV-thermal denaturation is a simple optical method widely employed for determination of DNA stability and interaction with ligands. Thermal denaturation of DNA and DNA-ligand complex is usually monitored at 260 nm. These data are generally presented as a function of the absorption increase of DNA alone with no consideration of the temperature dependent hyperchromism of the free ligand. Since not every ligand has absorption at 260 nm, usually this property of the ligand is ignored. Here, we report the temperature dependent hyperchromicity exhibited by Hoechst 33258 in the presence and absence of DNA. The presence of Hoechst, added to the duplex (monophasic profile, T(m)=75 degrees C) in various ratios generates a new transition at lower temperature displaying biphasic thermal transition profiles. We attributed this new transition (hyperchromic), a mere contribution from Hoechst, which might exist in aggregated forms. The extent of drug aggregation/self-association is concentration dependent. We suggest that prior to UV-melting studies the thermal dependence of the free ligand should be investigated.     

Spatial resonance in a small artery excited by vibration input as a possible mechanism to cause hand–arm vascular disorders

Hand–arm vibration syndrome (HAVS) is collectively a vasospastic and neurodegenerative occupational disease. One of the major symptoms of HAVS is vibration white finger (VWF) caused by exaggerated vasoconstriction of the arteries and skin arterioles. While VWF is a very painful and costly occupational illness, its pathology has not been well understood. In this study a small artery is modeled as a fluid filled elastic tube whose diameter changes along the axial direction. Equations of motion are developed by considering interactions between the fluid, artery wall and soft-tissue bed. It is shown that the resulting wave equation is the same as that of the basilar membrane in the cochlea of mammals. Therefore, the artery system shows a spatial resonance as in the basilar membrane, which responds with the highest amplitude at the location determined by the vibration frequency. This implies that a long-term use of one type of tool will induce high-level stresses at a few identical locations of the artery that correspond to the major frequency components of the tool. Hardening and deterioration of the artery at these locations may be a possible cause of VWF.     

Unexpected observations during the total synthesis of calothrixin B–sodium methoxide as a source of hydride

During the total synthesis of calothrixin B, various novel and unexpected results were noticed such as cleavage of C–N bond in imine using sodium cyanoborohydride, sodium methoxide as a hydride source for reduction, deformylation in the presence of bromine, and deacylation using ceric ammonium nitrate (CAN). A detailed mechanism has been proposed for the unexpected results and a few of them are generalized. Temperature dependent NMR studies have been carried out for confirmation of the structure of one of the intermediates in the synthetic sequence.     

3D CoMFA,CoMSIA, topomer CoMFA and HQSAR studies on aromatic acid esters for carbonic anhydrase inhibitory activity

Molecular modelling studies [comparative molecular field analysis (CoMFA), comparative molecular similarity indices analysis (CoMSIA), topomer CoMFA and hologram quantitative structure–activity relationship (HQSAR)] have been performed on the series of 28 molecules belonging to the series of aromatic acid ester derivatives for their carbonic anhydrase inhibitory activity. The model exhibited good correlation coefficient (r²) and cross‐validated correlation coefficient (q²) for CoMFA, CoMSIA and HQSAR methods. On the basis of the findings from all these studies, a structure–activity relationship was established. Copyright © 2013 John Wiley & Sons, Ltd.     

Liquid-liquid equilibrium in the toluene-methyl ethyl ketone-water system

For the toluene-methyl ethyl ketone-water system the liquid-liquid equilibrium tie-line data have been determined at 40 and 0°C and the binodal curve for this system has been determined at 40, 0 and −10°C. The tie-line data at 40 and 0°C could be correlated with good accuracy using NRTL and UNIQUAC model equations.     

Efficient enantioselective synthesis of (+)-sclareolide and (+)-tetrahydroactinidiolide: chiral LBA-induced biomimetic cyclization

An efficient enantioselective synthesis of the lactones (+)-sclareolide and (+)-tetrahydroactinidiolide has been achieved through Lewis acid-assisted chiral Brønsted acid-induced enantioselective cyclization of terpenic carboxylic acids. The reaction sequence involved the [2,3] sigmatropic rearrangement of an allylic alcohol and biomimetic cyclization of terpenic acid in the presence of (R)-2-benzyloxy-2′-hydroxy-1,1′-binaphthyl and tin tetrachloride as key steps. The cyclization gave lactones in good yield and with high enantiomeric excess.     

Boerhavia diffusa plant extract can be a new potent therapeutics against mutant nephrin protein responsible for type1 nephrotic syndrome: Insight into hydrate-ligand docking interactions and molecular dynamics simulation study

Nephrotic syndrome type 1 is an inherited condition in which mutation of NPHS1 gene, which encodes nephrin protein, results increase permeability of glomerular capillary wall for macromolecules causes heavy proteinuria, hypoproteinemia, and edema. Nephrotic syndrome patients are resistant to steroid and immunosuppressive treatment. Natural products have traditionally been used to treat a number of chronic diseases. Present study was focused to investigate potency of different phytochemicals found in Boerhavia diffusa (B.diffusa) plant against mutant nephrin protein. The study involves virtual screening of total 66 bioactive compounds from B.diffusa plant against wild type and mutant models of Ig4 domain of nephrin protein through AutoDock raccoon. Based on binding energy and drug-likeness property, seven phytocompounds were screened. Hydrate-ligand docking (addition of explicit waters in ligands) method was used to select potential phytocompounds that could bind to mutant model of Ig4 domain of nephrin protein. For further prediction, molecular dynamics simulations with 100ns trajectory of Ig4 domain of nephrin protein in glycolipid bilayer membrane for systems such as wild, mutant, mutant model complex with boeravinone M and mutant model complex with boeravinone E were thoroughly studied. Hydrate-ligand docking result predicted boeravinone M and boeravinone E have shown better binding performance with mutant model. It causes due to hydration force field that measures entropy and enthalpy for each water molecule separately, allowing for more exact estimations of their contribution to ligand-protein interaction. Boeravinone E shows lowest short-range Lennard-Jones (LJ-SR) interaction energies of ?47.78 ± 12.7 kJ/mol. The results showed reduced compactness and stability nature of mutant model of Ig4 domain of nephrin protein, however, binding with boeravinone E has effectively modulated its stability and function by increasing its compactness. Current study may provide insight into therapeutic development of boeravinone E as a potential inhibitor against NPHS1in near future.     

Synthesis of 2-phenyl pyridine derivatives from aryl ketones and 1,3-diaminopropane using palladium acetate as a catalyst

A simple and efficient method for the synthesis of 2-phenyl pyridine via cyclization of aryl ketone with 1,3-diaminopropane using palladium acetate is established. This method is mild, operationally simple, involves short reaction time and involves easy workup procedure to afford the corresponding 2-phenyl pyridines in moderate to good yield.     

Insights into Structural Modifications of Valproic Acid and Their Pharmacological Profile

Valproic acid (VPA) is a well-established anticonvulsant drug discovered serendipitously and marketed for the treatment of epilepsy, migraine, bipolar disorder and neuropathic pain. Apart from this, VPA has potential therapeutic applications in other central nervous system (CNS) disorders and in various cancer types. Since the discovery of its anticonvulsant activity, substantial efforts have been made to develop structural analogues and derivatives in an attempt to increase potency and decrease adverse side effects, the most significant being teratogenicity and hepatotoxicity. Most of these compounds have shown reduced toxicity with improved potency. The simple structure of VPA offers a great advantage to its modification. This review briefly discusses the pharmacology and molecular targets of VPA. The article then elaborates on the structural modifications in VPA including amide-derivatives, acid and cyclic analogues, urea derivatives and pro-drugs, and compares their pharmacological profile with that of the parent molecule. The current challenges for the clinical use of these derivatives are also discussed. The review is expected to provide necessary knowledgebase for the further development of VPA-derived compounds.