From the X-ray compact structure to the elongated form of the full-length MMP-2 enzyme in solution: a molecular dynamics study

Current understanding on the collagenolytic activity performed by the MMPs assumes some degree of relative motion between the catalytic and the hemopexin-like domains of the enzyme. However, all the crystal structures available for the full-length enzymes display a compact arrangement of the protein domains. Herein, we employ Molecular Dynamics simulations to investigate the structure of the full-length MMP-2 enzyme in aqueous solution. This simulation, together with previous experimental results that have been obtained very recently for the MMP-9 and MMP-12 enzymes, gives strong support to the hypothesis that the interdomain dynamics of the MMP enzymes in solution can result in a manifold of conformations including some structures with a large interdomain separation. The simulation of MMP-2 provides also a detailed molecular picture of the structures involved in the transition from the compact X-ray arrangement to the extended form in solution. Such information could be helpful in future studies of the regulation and/or the collagenolytic activity of these important enzymes.     

Copper (II) complexes of sterically hindered o-diphenol derivatives: synthesis, characterization and microbiological studies

Cu (II) complexes with the sterically hindered diphenol derivatives 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzenetriol (II) and the sulfur-containing 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements. Compounds I–III can coordinate in their singly deprotonated forms and act as bidentate ligands. These compounds yield Cu (II) complexes of the stoichiometry Cu(L)₂, which have square planar geometry (g_| > g_⊥ > g_e). Unlike them, compound IV behaves as a terdentate ligand, and its complex Cu(L^IV)₂ has distorted octahedral geometry. According to ESR data, only the Cu(L^II)₂ complex contains a very small amount of phenoxyl radicals. Antimicrobial activities of these ligands and their respective Cu (II) complexes have been determined with respect to Gram-positive and Gram-negative bacteria, as well as on yeasts. Their phytotoxic properties against Chlorella vulgaris 157 were also examined.     

Electrochemical determination of chromium(VI) using metallic nanoparticle-modified carbon screen-printed electrodes

Carbon screen-printed electrodes (CSPEs) modified with metal nanoparticles present an interesting alternative in the determination of chromium(VI) by differential pulse voltammetry (DPV).Metallic silver and gold nanoparticle deposits have been obtained by electrochemical deposition. Scanning electron microscopy measurements show that the electrochemically synthesized silver and gold nanoparticles are deposited in aggregated form.The detection limit for the analytical procedures developed in this work were 8.5 × 10⁻⁷ and 4.0 × 10⁻⁷ M for silver and gold nanoparticle-modifed CSPE, respectively.In terms of reproducibility, the precision of the above-mentioned method was calculated at 6.7% in %R.S.D. values for silver and 3.21% for gold nanoparticle CSPE.     

GeO2 natrolite-type infinite four and eight R-containing layers in a 2D pure-Ge framework: Ge3O5(OH)4[C2N2H10

A new two-dimensional framework germanate, Ge3O5(OH)4[C2N2H10] (denoted ICMM-8), with a 3:9 Ge:O ratio has been synthesized, using a mixture of pyridine, water, and ethanol as the solvent and 1,4-diazabicyclo[2.2.2]octane and ethylenediamine as the structure-directing agents, under solvothermal conditions. The structure was determined by single-crystal X-ray diffraction. In this new compound, the GeO2 natrolite-type infinite four and eight R-containing layers appears for the first time in a pure GeO2 framework. The total 2D structure is built up from SBU-6, four tetrahedra, and two octahedra. The hydroxyl groups occupy four positions of each octahedral germanium atom. The compound is characterized by IR spectra and TGA-DTA. Crystal data: Ge3O5(OH)4[C2N2H10], monoclinic space group P2(1)/c; a = 11.3570(9) Angstroms, b = 8.8819(7) Angstroms, c = 9.9200(8) Angstroms, beta = 90.710(1), V = 1000.6(1) Angstroms(3), Z = 4, R(1) = 0.044 (I > 2(I)), and wR(2) = 0.1051 (all data).     

Distinct dynamic behaviors of water molecules in hydrated pores

Water molecules confined inside narrow pores are of great importance in understanding the structure, stability, and function of water channels. Here we report that besides the H-bonding water that structures the pore, the permanent presence of a significant, fast-moving fraction of incompletely H-bonded water molecules inside the pore should control the free entry and exit of water. This is achieved by means of complementary DSC and solid-state NMR studies. We also present compelling evidence from X-ray diffraction data that the cluster formed by six water molecules in the most stable cage-like structure is sufficiently hydrophobic to be stably adsorbed in a nonpolar environment.     

The Bioluminescence Resonance Energy Transfer from Firefly Luciferase to a Synthetic Dye and its Application for the Rapid Homogeneous Immunoassay of Progesterone

The sensitive BRET system for the homogeneous immunoassay of a low‐molecular weight antigen was developed using progesterone as an example. Two thermostable mutants of the Luciola mingrelica firefly luciferase (Luc)—the “red” mutant with λ_max.em = 590 nm (RedLuc) and the “green” mutant with λ_max.em = 550 nm (GreenLuc)—were tested as the donors. The water‐soluble Alexa Fluor 610× (AF) dye was selected as the acceptor because its two absorption maxima, located at 550 and 610 nm, are close to the bioluminescence maxima of the GreenLuc and RedLuc, respectively. The methods for the synthesis of the luciferase–progesterone (Luc–Pg) conjugate and the conjugate of the dye and the polyclonal antiprogesterone antibody (AF–Ab) were developed. Both conjugates retained their functional properties, had high antigen–antibody binding activity, and demonstrated a high BRET signal. The homogeneous immunoassay system based on the BRET from the firefly luciferase to the synthetic dye was established to assay progesterone as a model antigen. Optimization of the assay conditions, the composition of the reaction mixture, and the concentrations of the donor and the acceptor made it possible to reach the minimum detectable progesterone concentration of 0.5 ng mL^?1.     

The Calculus of HLB Values of Polyoxyethylene Fatty Acid Esters from Quality Control Data

In this article, we obtained equations that permit us to calculate the hydrophilic-lipophilic balance (HLB) value of polyoxyethylene esters from quality control data of the raw materials (fatty acids and polyethylene glycol) and the finished product (surfactant). These data include the acid value of the fatty acid, the hydroxyl value of the polyethylene glycol, and the hydroxyl value of the surfactant. These calculations permit us, moreover, to know the mean molecular masses of fatty acids, of polyethylene glycol, of monoester and diester, and the proportion of polyoxyethylene monoester and polyoxyethylene diester.