One-bead-one-inhibitor-one-substrate screening of neuraminidase activity

Given the eminent threat of a 21st century flu pandemic, the search for novel antiviral compounds is an increasingly important area of research. Recent developments in antiviral research have established the viability of targeting viral neuraminidase (NA), an enzyme that cleaves sialic acid from the cell-surface-mediating passage of the virus in the respiratory tract. N-acetyl neuraminic acid (NeuAc) is the substrate for NA, and analogues of this core structure have been commercialized as antiviral therapeutics. Recent studies have established that this system is well suited for combinatorial approaches to drug discovery. An important step in the process is to develop solid-phase screening technologies. The feasibility of performing competitive solid-phase NA assays is reported herein. Initially, a fluorogenic NeuAc substrate was immobilized on solid support, and the ability of three NAs (Clostridium perfringens, Salmonella typhimurium, and Vibrio cholerae) to cleave the substrate was shown to be analogous to solution-phase assays. The solid support was then bifunctionalized with the fluorogenic NeuAc substrate and one of two known inhibitors (DANA and Zanamivir). The ability of NA to cleave NeuAc from the solid support when simultaneously presented with an inhibitor was shown to be enzyme dependent. As expected, simultaneous presentation of NeuAc and DANA, a nonspecific inhibitor, led to diminished activity for all three enzymes tested. In contrast, dual presentation of NeuAc and the selective inhibitor Zanamivir only showed significant activity against Vibrio cholerae.     

A priori molecular descriptors in QSAR: a case of HIV-1 protease inhibitors. II. Molecular graphics and modeling

Molecular graphics and modeling methods illustrated the chemical background of the a priori approach from part I, and visualized steric and electronic enzyme-inhibitor relationships at qualitative and quantitative level for 34 and its derivatives. The enzyme-inhibitor electron density overlap occurs at 1.5–5.5 Å cut-off distance, beyond van der Waals radii. Derivatives of 34 exhibit linear relationships between biological activity, molecular size and number of intermolecular interactions.     

Performance of water-based foams affected by chemical inhibitors to retard spontaneous combustion of coal

The micelle generating process of the sodium dodecyl sulfate(SDS) solution with the addition of chemical inhibitors was elucidated using phase separation model, and the descending order of the capacity for the selected chemical inhibitors to reduce the critical micelle concentrations of the solution are Mg Cl_2, Ca Cl_2,NH_4HCO_3 and NH_4Cl. The data to quantitatively describe the foam decay process, including foaming ratio,foam life and decay behaviors, was obtained by pressure measuring system. The results indicate that chemical inhibitors can improve the solution foamability. The capacity of the inhibitors to enhance the solution foamability is sorted as NH_4 Cl, NH_4HCO_3, Mg Cl2 and Ca Cl_2 which can distinctly improve the foam stability as well. The capacity of the inhibitors to enhance the SDS foam stability can be arranged as Mg Cl_2, NH_4 Cl, NH_4HCO_3 and Ca Cl_2. It is observed that the gravity drainage plays a leading role in the increase of proportion of diffusion drainage. The oxidation dynamic parameters of the coal samples treated by inhibition foams were investigated using thermal analysis technique, and their synergistic effects on inhibiting coal oxidation were explored.     

Is subcooling the right driving force for testing low-dosage hydrate inhibitors?

The degree of subcooling is usually used as the driving force for hydrate formation; however, it does not encompass the effect of pressure. A comprehensive driving force for hydrate formation is a function of pressure, temperature, and gas composition; however, its calculation is not as simple as that of subcooling. In this work, by application of the two latest driving force expressions for hydrate formation, the relationships between subcooling and the true driving force at different conditions for pure gas-water and natural gas-water systems are analysed. The effect of pressure on the induction time in the presence and absence of a kinetic inhibitor have been tested at similar degrees of subcooling.The results show that for pure gas-water systems subcooling is proportional to the driving force, with a good approximation over a wide pressure range at isothermal conditions. However, for multicomponent systems (e.g., natural gases), the driving force is more than that suggested by subcooling at some pressures. Changes of driving force with pressure at a constant degree of subcooling for the above systems have been presented. The results show that the pressure has no significant effect on the driving force (at a constant degree of subcooling) above a certain pressure range. The experimental results show that in a natural gas-water system at constant degree of subcooling the induction time is not significantly affected by pressure. However, in the presence of the kinetic inhibitor tested in this study, high-pressure conditions decreased the induction time.     

水合物动力学抑制研究现状

着重评述了二类低用量水合物抑制剂,即动力学抑制剂和防聚剂的抑制机理方面的理论研究成果,以及抑制性能方面的实验研究成果。简要介绍了低用量水合物抑制剂的应用状况。根据水合物动力学抑制的研究现状,指出了可作为今后研究重点的5个方面。     

New cis-configured aziridine-2-carboxylates as aspartic acid protease inhibitors

A series of 52 cis‐configured 1‐alkyl‐3‐phenylaziridine‐2‐carboxylates were synthesized as new pseudo‐irreversible inhibitors of Candida albicans secreted aspartic acid protease 1 (SAP1), SAP2, SAP3, and SAP8. Some of the compounds, which were obtained as diastereomers with S,S‐ and R,R‐configured aziridine rings by Cromwell synthesis of racemic (2R,3S+2S,3R)‐dibromophenylpropionic acid ester with amines, followed by ester hydrolysis and coupling to hydrophobic amino acid esters, were separated by preparative HPLC. The absolute configuration of the aziridine ring was assigned by a combination of experimental circular dichroism (CD) investigations and quantum chemical CD calculations. In agreement with previous docking studies, the diastereomers all exhibit similar activity. The compounds were found to be more active against the related mammalian enzyme cathepsin D, presumably due to productive interactions of the N‐alkyl substituent with the highly lipophilic S2 pocket. The most active inhibitors ( 5 , 9 , 10 , 21 , and 28 ), characterized by benzyl, cyclohexylmethyl, tert‐butyl, or 1,4‐dimethylpentyl moieties at the aziridine nitrogen atom, exhibit k_2nd values between 500 and 900×10³ M ^?1 min^?1 and K_i values near or below 1 μM for cathepsin D.     

Benzimidazolium salts as small, nonpeptidic and BBB-permeable human prolyl oligopeptidase inhibitors

Prolyl oligopeptidase (POP) is a cytosolic serine peptidase that hydrolyzes proline-containing peptides at the carboxy terminus of proline residues. This peptidase has gained importance as a target for the treatment of cognitive disturbances of patients with neuropsychiatric diseases. Our research addresses the identification of POP inhibitors from a small focused library of polar heterocyclic compounds arising from multicomponent reactions. Two selective POP-specific inhibitors were identified on the basis of their inhibition of dipeptidyl peptidase IV. The most active compounds were evaluated for their in vitro transport through the blood-brain barrier (BBB) using a parallel artificial membrane permeability assay. Our results show for the first time that benzimidazolium salts are new POP-inhibitory scaffolds with properties of solubility, specificity, and lipophilicity that may allow them to cross the BBB by passive diffusion. These findings constitute an excellent starting point to synthesize new POP inhibitors with enhanced properties.     

Aldimines — Effective Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution

New and effective aldimine types of corrosion inhibitors namely, N-methylidene octylamine (MOA), N-ethylidene octylamine (EOA) and N-propylidene octylamine (POA) have been synthesized. Their inhibition efficiency was investigated for the corrosion of mild steel in 1 M HCl solution by various corrosion monitoring techniques. A preliminary screening of the inhibition efficiency of the inhibitors was carried out by weight loss and gasometric studies. They were found to behave as good inhibitors in 1 M HCl solution. Potentiodynamic polarization measurements show that aldimines are mixed type inhibitors. The extent of the decrease in the hydrogen permeation current through the mild steel surface was studied by the hydrogen permeation technique and it was found that the decrease was in the order POA > EOA > MOA. Double layer capacitance and charge transfer resistance values were derived from Nyquist plots obtained from AC impedance studies. The adsorption of these compounds on mild steel from 1 M HCl solution obeys the Temkin adsorption isotherm.