Efficacy and Limitations of Chemically Diverse Small-Molecule Enzyme-Inhibitors against the Synergistic Coagulotoxic Activities of Bitis Viper Venoms

Snakebite remains a significant public health burden globally, disproportionately affecting low-income and impoverished regions of the world. Recently, researchers have begun to focus on the use of small-molecule inhibitors as potential candidates for the neutralisation of key snake venom toxins and as potential field therapies. Bitis vipers represent some of the most medically important as well as frequently encountered snake species in Africa, with a number of species possessing anticoagulant phospholipase A₂ (PLA₂) toxins that prevent the prothrombinase complex from inducing clot formation. Additionally, species within the genus are known to exert pseudo-procoagulant activity, whereby kallikrein enzymatic toxins cleave fibrinogen to form a weak fibrin clot that rapidly degrades, thereby depleting fibrinogen levels and contributing to the net anticoagulant state. Utilising well-validated coagulation assays measuring time until clot formation, this study addresses the in vitro efficacy of three small molecule enzyme inhibitors (marimastat, prinomastat and varespladib) in neutralising these aforementioned activities. The PLA₂ inhibitor varespladib showed the greatest efficacy for the neutralisation of PLA₂-driven anticoagulant venom activity, with the metalloproteinase inhibitors prinomastat and marimastat both showing low and highly variable degrees of cross-neutralisation with PLA₂ anticoagulant toxicity. However, none of the inhibitors showed efficacy in neutralising the pseudo-procoagulant venom activity exerted by the venom of B. caudalis. Our results highlight the complex nature of snake venoms, for which single-compound treatments will not be universally effective, but combinations might prove highly effective. Despite the limitations of these inhibitors with regards to in vitro kallikrein enzyme pseudo-procoagulant venom activity, our results further support the growing body of literature indicating the potential use of small molecule inhibitors to enhance first-aid treatment of snakebite envenoming, particularly in cases where hospital and thus antivenom treatment is either unavailable or far away.     

A rapid heating and high magnetic field thermal analysis technique

Journal of Thermal Analysis and Calorimetry - A new thermal analysis technique is described that allows measurements to be performed on bulk samples at extreme heating and cooling rates and in high...     

AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_(1-x) Fe_2O_4和Ni_xMn_(1-x)Fe_2O_4立方相中的Zn~(2+)、Ni~(2+)、Mn~(2+)以及Fe~(3+)在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn~(2+)完全占据在8a亚晶格上,Fe~(3+)完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe~(3+)0.09Mn~(2+)0.91)[Fe~(3+)1.91Mn~(2+)0.09]O_4,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe~(3+)0.11Mn~(2+)0.89)[Fe~(3+)1.89Mn~(2+)0.11]O_4,均与实验结果符合较好。在锌铁氧体中,室温下Zn~(2+)完全占据在8a亚晶格上,Fe~(3+)完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn~(2+)和Fe~(3+)发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe~(3+)在室温下占据在8a亚晶格上,Ni~(2+)与剩下另一半的Fe~(3+)共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学模型研究了立方相尖晶石结构的Zn_xMn_(1-x)Fe_2O_4、Ni_xMn_(1-x)Fe_2O_4复合体系中阳离子占位行为与热处理温度对占位的影响规律。     

Application and validation of an ion-exchange high-performance liquid chromatographic method for measuring adenine nucleotides, creatine and creatine phosphate in mouse brain

We have modified and applied an ion-exchange high-performance liquid chromatographic method for measuring adenine nucleotides (adenosine monophosphate, adenosine diphosphate and adenosine triphosphate) as well as creatine and creatine phosphate in brain tissue. There was a linear relationship between the area of each peak and the amount of standard injected onto the column in the concentration range 0.5-25 nmol per 50 microliters. The concentrations of creatine phosphate and creatine were not stable in a standard mixture for 20 h at 4 degrees C unless the pH of the standard mixture was adjusted to neutral. We therefore strongly recommended the neutralization of all standard mixtures and samples before storage. The measurements of adenine nucleotides, creatine and phosphate in control mouse brain determined by this method agreed well with an enzymic method of nucleotide measurement. Furthermore, both methods detected similar decreases in the concentrations of adenosine triphosphate and creatine phosphate, together with concomitant increases in the concentrations of adenosine diphosphate, adenosine monophosphate and creatine when mice were placed under anoxic conditions (either 30 s or 2 min); these changes were greater after 2 min of anoxia than after 30 s of anoxia.     

Spectroscopic properties of trichlorofluoromethane CCl(3)F calculated by density functional theory

Density functional theory is used to generate local potential energy surfaces in normal coordinates for several chlorine isotopomers of trichlorofluoromethane (CCl(3)F, CFC11). An examination of predicted structures suggested that the PBE0 functional would be suitable. Anharmonic surfaces around the equilibrium geometries are reported, as determined by energies, gradients, and second derivatives. Vibrational levels for fundamentals, overtones and combination bands are reported, as well as harmonic frequencies, anharmonic constants, rotational constants, isotope shifts, and infrared intensities. These are compared with experimental information.     

Synthesis of tetra-ortho-substituted, phosphorus-containing and carbonyl-containing biaryls utilizing a Diels-Alder approach

The application of the Diels-Alder approach to biaryls (DAB) is described for the synthesis of tetra-ortho-substituted biaryl compounds containing orthogonally functionalized substituents. The syntheses of phosphorus-containing, disubstituted alkynes and carbonyl-containing, disubstituted alkynes were accomplished in two to three steps from commercially available reagents. Subsequent Diels-Alder cycloadditions with a range of oxygenated dienes yielded the target biaryls. Further functionalization through palladium-couplings is demonstrated on the phosphorus-containing biaryls. In addition, selective manipulation of each of the remaining ortho substituents on the phosphorus-containing biaryls is demonstrated. One of these phosphorus-containing derivatives is utilized as a highly active catalyst for Suzuki coupling. For the carbonyl-containing series, a wide range of dienophile substituents were screened including esters, ketones, and amides. The key Diels-Alder cycloadditions proceeded smoothly with the commercially available 1-methoxy-1,3-cyclohexadiene to yield the resultant tetra-ortho-substituted biaryls with excellent regioselectivity. The scope of the cycloaddition process was also explored on the carbonyl-containing dienophiles with a series of cyclic dienes. Acyclic dienes were also screened; however, they did not prove effective in the Diels-Alder process with the carbonyl-containing acetylenes. The ability to isolate enantiomerically pure biaryl atropisomers using a benzyl oxazolidinone is disclosed. Finally, the subsequent conversion to an axially chiral anilino alcohol is also reported.     

Conducting polymer diffraction gratings on gold surfaces created by microcontact printing and electropolymerization at submicron length scales

Conducting polymer diffraction gratings on Au substrates have been created using microcontact printing of C18-alkanethiols, followed by electropolymerization of either poly(aniline) (PANI) or poly(3,4-ethylenedioxythiophene) (PEDOT). Soft-polymer replicas of simple diffraction grating masters (1200 lines/mm) were used to define the alkanethiol template for polymer growth. Growth of PANI and PEDOT diffraction gratings was followed in real time, through in situ tapping-mode atomic force microscopy, and by monitoring diffraction efficiency (DE) as a function of grating depth. DE increased as grating depth increased, up to a limiting efficiency (13-26%, with white light illumination), defined by the combined optical properties of the grating and the Au substrate, and ultimately limited by the loss of resolution due to coalescence of the polymer films. Grating efficiency is strongly dependent upon the grating depth and the refractive index contrast between the grating material and the surrounding solutions. Both PEDOT and PANI gratings show refractive index changes as a function of applied potential, consistent with changes in refractive index brought about by the doping/dedoping of the conducting polymer. The DE of PANI gratings are strongly dependent on the pH of the superstrate solution; the maximum sensitivity (DeltaDE/DeltapH) is achieved with PANI gratings held at +0.4 V versus Ag/AgCl, where the redox chemistry is dominated by the acid-base equilibrium between the protonated (emeraldine salt) and deprotonated (emeraldine base) forms of PANI. Simulations of DE were conducted for various combinations of conducting polymer refractive index and grating depth, to compute sensitivity parameters, which are maximized when the grating depth is ca. 50% of its maximum obtainable depth.     

A comparative investigation of the fatty acid compositions of the seeds of a number of lines of a genetic collection of Gossypium hirsutum

A comparative analysis has been made of the amounts of lipids and their fatty-acid compositions in the seeds of the lines of agenetic collection of cotton plants of the speciesGossypium hirsutum and their hybrids and the variety Tashkent-1. The results obtained on the fatty-acid compositions of some hybrids make it possible to recommend the use of individual lines of cotton plants as donors for improving the food-value indices of cottonseed oil.Institute of Chemsitry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 173–176, March–April, 1991.     

Crystal structure and DFT calculations of Cp2NbH(SiIMe2)(SiFMe2): an asymmetric bis(silyl) niobocene hydride complex

An asymmetric bis(silyl) niobocene hydride complex, namely, bis(η⁵-cyclopentadienyl)(fluorodimethylsilyl)hydrido(iododimethylsilyl)niobium, [Nb(C₅H₅)₂(C₂H₆FSi)(C₂H₆ISi)H] or Cp₂NbH(SiIMe₂)(SiFMe₂), has been studied to determine the effect of the silyl ligand on the position of the hydride attached to the Nb atom. It has been shown that when a Group 17 atom is substituted onto one of the silyl ligands, there is a greater interaction between the hydride and this ligand, as demonstrated by a shorter Si…H distance. In the present work, we have investigated the effect when the silyl ligands are substituted by different Group 17 atoms. We present here the structure and DFT calculations of Cp₂NbH(SiIMe₂)(SiFMe₂), showing that the position of the hydride is located between the two silyl ligands. The results from our investigation show that the hydride is closer to the silyl ligand that is substituted by fluorine.     

Ionization of five aqueous fluorobenzoic acids: Conductance and thermodynamics

The three monofluorobenzoic acids together with 2,4-difluoro and 2,6-difluorobenzoic acids in aqueous solution are the subject of precision conductance measurements. The experimental data are analyzed to give ionization constants and limiting conductances at temperatures from 0 to 100°C. Walden products for the acid anions are derived from the limiting conductances while the ionization consatants are fitted by statistical methods to the function pK _a (m)=A+B/T+ C logT+DT. Only the 2,6- acid requires the fourth term of the function to fit the data to a precision of better than 0.03%. Mathematical analysis of the pK function gives the standard changes in enthalpy, entropy, and heat capacity. All the acids studied are more acidic than the parent, benzoic acid, as well as more acidic than the isoelectronic methylbenzoic acids. In general the increased acidity is tied to decreases in enthalpy while entropy changes on ionization differn little from those found for the parent acid.