Diethylpyrocarbonate, a Histidine Selective Reagent, Causes Structural Alteration of Rat Ovarian LH/hCG Receptor

Abstract. Treatment of íat ovanan membiane-bound and Tnton X-100 solubilized LH/hCG íeceptoi with a histidme-specific icagent diethylpyiocaibonate (DEPC) íesulted m macti\ation of the ability of the íeccptoi to bind hCG The paitial íe-veisibihťv of this inhibition by hydioxylamme domonstiated that histidine losidues aie involved m hCG-ieceptoi binding Fhioies(ence quenching expeiiments nidi cated that DEPC did not change the accessibihty of fiuoiophoies foi aciylamide Alterations of quenchiiig íate goneially suggest exposuie of tivptophanvl íesidues Modification of histidjl íesidues was connected with an alteiation of the physical state of ovanan membianes Membiane lipid iigicht\ was dec leased aftei DEPC íe action Theimal peitmbation techniques won used to monitoi stnutuial (lianges m the ícceptoi clue to the action of DEPC on membianes Heat mactnation of hCG-bmdmg sites demonstiated that theie was a signmc ant destabilization of the LH/hCG íeeeptoi stmctuie when the inembianes weio tieated with DEPC Thei mal dcstabih/ation pioduced h\ 5 mmol/1 DEPC ( ausc d a dec lease m T^, 0 \ allies bv about 12°C These íesults suggest that histidine lesidues aie lo< ated at the binding sites of the íeeeptoi and that they aie also imohed m alteiations of membiane piotems the stiuctuial mtcgiitv of w Inch sec ondanly influences the ae ce^ssibihty oi the LH/hCG íeceptoi Key words: Diethv lpyiocaibonate LH/hCG nceptois Theimal mat tnation Fluoiesc enc e polaii/atio

Challenges to evidence synthesis and identification of data gaps in human biomonitoring

The increasing number of human biomonitoring (HBM) studies undertaken in recent decades has brought to light the need to harmonise procedures along all phases of the study, including sampling, data collection and analytical methods to allow data comparability. The first steps towards harmonisation are the identification and collation of HBM methodological information of existing studies and data gaps. Systematic literature reviews and meta-analyses have been traditionally put at the top of the hierarchy of evidence, being increasingly applied to map available evidence on health risks linked to exposure to chemicals. However, these methods mainly capture peer-reviewed articles, failing to comprehensively identify other important, unpublished sources of information that are pivotal to gather a complete map of the produced evidence in the area of HBM. Within the framework of the European Human Biomonitoring Initiative (HBM4EU) initiative—a project that joins 30 countries, 29 from Europe plus Israel, the European Environment Agency and the European Commission—a comprehensive work of data triangulation has been made to identify existing HBM studies and data gaps across countries within the consortium. The use of documentary analysis together with an up-to-date platform to fulfil this need and its implications for research and practice are discussed

Thermal Stability of the Human Immunodeficiency Virus Type 1 (HIV-1) Receptors, CD4 and CXCR4, Reconstituted in Proteoliposomes

BACKGROUND: The entry of human immunodeficiency virus (HIV-1) into host cells involves the interaction of the viral exterior envelope glycoprotein, gp120, and receptors on the target cell. The HIV-1 receptors are CD4 and one of two chemokine receptors, CCR5 or CXCR4. METHODOLOGY/PRINCIPAL FINDINGS: We created proteoliposomes that contain CD4, the primary HIV-1 receptor, and one of the coreceptors, CXCR4. Antibodies against CD4 and CXCR4 specifically bound the proteoliposomes. CXCL12, the natural ligand for CXCR4, and the small-molecule CXCR4 antagonist, AMD3100, bound the proteoliposomes with affinities close to those associated with the binding of these molecules to cells expressing CXCR4 and CD4. The HIV-1 gp120 exterior envelope glycoprotein bound tightly to proteoliposomes expressing only CD4 and, in the presence of soluble CD4, bound weakly to proteoliposomes expressing only CXCR4. The thermal stability of CD4 and CXCR4 inserted into liposomes was examined. Thermal denaturation of CXCR4 followed second-order kinetics, with an activation energy (E(a)) of 269 kJ/mol (64.3 kcal/mol) and an inactivation temperature (T(i)) of 56°C. Thermal inactivation of CD4 exhibited a reaction order of 1.3, an E(a) of 278 kJ/mol (66.5 kcal/mol), and a T(i) of 52.2°C. The second-order denaturation kinetics of CXCR4 is unusual among G protein-coupled receptors, and may result from dimeric interactions between CXCR4 molecules. CONCLUSIONS/SIGNIFICANCE: Our studies with proteoliposomes containing the native HIV-1 receptors allowed an examination of the binding of biologically important ligands and revealed the higher-order denaturation kinetics of these receptors. CD4/CXCR4-proteoliposomes may be useful for the study of virus-target cell interactions and for the identification of inhibitors

From science to policy: How European HBM indicators help to answer policy questions related to phthalates and DINCH exposure

Within the European Human Biomonitoring (HBM) Initiative HBM4EU we derived HBM indicators that were designed to help answering key policy questions and support chemical policies. The result indicators convey information on chemicals exposure of different age groups, sexes, geographical regions and time points by comparing median exposure values. If differences are observed for one group or the other, policy measures or risk management options can be implemented. Impact indicators support health risk assessment by comparing exposure values with health-based guidance values, such as human biomonitoring guidance values (HBM-GVs). In general, the indicators should be designed to translate complex scientific information into short and clear messages and make it accessible to policy makers but also to a broader audience such as stakeholders (e.g. NGO's), other scientists and the general public. Based on harmonized data from the HBM4EU Aligned Studies (2014-2021), the usefulness of our indicators was demonstrated for the age group children (6-11 years), using two case examples: one phthalate (Diisobutyl phthalate: DiBP) and one non-phthalate substitute (Di-isononyl cyclohexane-1,2- dicarboxylate: DINCH). For the comparison of age groups, these were compared to data for teenagers (12-18 years), and time periods were compared using data from the DEMOCOPHES project (2011-2012). Our result indicators proved to be suitable for demonstrating the effectiveness of policy measures for DiBP and the need of continuous monitoring for DINCH. They showed similar exposure for boys and girls, indicating that there is no need for gender focused interventions and/or no indication of sex-specific exposure patterns. They created a basis for a targeted approach by highlighting relevant geographical differences in internal exposure. An adequate data basis is essential for revealing differences for all indicators. This was particularly evident in our studies on the indicators on age differences. The impact indicator revealed that health risks based on exposure to DiBP cannot be excluded. This is an indication or flag for risk managers and policy makers that exposure to DiBP still is a relevant health issue. HBM indicators derived within HBM4EU are a valuable and important complement to existing indicator lists in the context of environment and health. Their applicability, current shortcomings and solution strategies are outlined

Selective Catalytic Cracking of Higher Alkenes

New type of zeolite catalyst of ZSM-5 type partially transformed to acidic form with improved selectivity has been developed in the study. After catalyst modification by cerium ion the selectivity was moreover increased. Catalytic cracking of 1-hexene to propylene was used as a test reaction. Kinetic model parameters of the reaction system were identified by AspenPlus software application. The catalyst deactivation kinetics was investigated too