Abstract A method is described for the simultaneous measurement of partial specific volumes and molecular weights proteins other substances by sedimentation equilibrium experiments in H2O D2O (or D2O18) solutions. In effect, a differential technique based upon change produced concentration distribution when density solution increased use D2O18). The equations used two parallel account deuterium exchange incorporation factor which changes only slightly different can be estimated with...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUltracentrifuge Studies with Absorption Optics. IV. Molecular Weight Determinations at the Microgram Level*H. K. Schachman and S. J. EdelsteinCite this: Biochemistry 1966, 5, 8, 2681–2705Publication Date (Print):August 1, 1966Publication History Published online1 May 2002Published inissue 1 August 1966https://pubs.acs.org/doi/10.1021/bi00872a029https://doi.org/10.1021/bi00872a029research-articleACS PublicationsRequest reuse permissionsArticle...

Exactly 50 years ago, biochemists raised the question of mechanism conformational change that mediates "allosteric" interactions between regulatory sites and biologically active in regulatory/receptor proteins. Do different conformations involved already exist spontaneously absence ligands (Monod-Wyman-Changeux), such complementary protein conformation would be selected to mediate signal transduction, or do particular induce receptor adopt best suited them (Koshland-Nemethy-Filmer-induced...

Abstract Human hemoglobin has been studied in parallel experiments on structure and function. Structure examined terms of the extent dissociation into subunits very dilute solutions by sedimentation velocity equilibrium with a scanning ultracentrifuge. Functional properties have evaluated two rapid kinetic approaches, stopped flow mixing deoxyhemoglobin carbon monoxide flash photolysis CO-hemoglobin. The indicate that tetrameric CO-hemoglobin dimers is accompanied transition from slow rate...

The standard model of eukaryotic ribosomal RNA (rRNA) genes involves tandem arrays with hundreds units in clusters, the nucleolus organizer regions (NORs). A first genomic overview for human cells is reported here these regions, which have never been sequenced their totality, by using molecular combing. rRNA-coding are examined fluorescence on single molecules DNA two specific probes that cover entire length. organization assumed rDNA a transcribed region followed nontranscribed spacer....

Abstract A method is described for determining the equilibrium constant of tetramer-dimer dissociation reaction unliganded hemoglobin. The based on large difference between ligand binding affinities dimer and tetramer, utilizes affinity dilute hemoglobin solutions as a sensitive assay fraction heme in dimeric state. CO containing 0.05 to 8.0 µm have been determined, show dependence concentration expected equilibrium. In 0.1 m phosphate, pH 7.0, this by 3 x 10-12 m. Experiments with 2.0 NaCl,...

G protein-coupled receptors are thought to mediate agonist-evoked signal transduction by interconverting between discrete conformational states endowed with different pharmacological and functional properties. In order address the question of multiple receptor states, we monitored rapid kinetics fluorescent neurokinin A (NKA) binding tachykinin NK2 receptors, in parallel intracellular calcium, using mixing equipment connected real time fluorescence detection. Cyclic AMP accumulation...

Neurotransmitters such as acetylcholine (ACh) and glycine mediate fast synaptic neurotransmission by activating pentameric ligand-gated ion channels (LGICs). These receptors are allosteric transmembrane proteins that rapidly convert chemical messages into electrical signals. activate LGICs interacting with an extracellular agonist-binding domain (ECD), triggering a tertiary/quaternary conformational change in the protein results opening of pore (IPD). However, molecular mechanism determines...

To identify the molecular determinants underlying pharmacological diversity of neuronal nicotinic acetylcholine receptors, we compared alpha7 homo-oligomeric and alpha4beta2 hetero-oligomeric receptors. Sets residues from regions initially identified within agonist binding site alpha4 subunit were introduced into site, carried by alpha7-V201-5HT3 chimera. Introduction 183-191 sequence (chimera C2) selectively increased apparent affinities for equilibrium ion channel activation acetylcholine,...

Oxygen binding curves (OEC) for red cell suspensions have a biphasic shape and reduced n50 values when the concentration of 2,3-diphosphoglycerate (DPG) is lowered by aging or experimental procedures. The mechanism abnormal OEC has been related to variations in activity free DPG. DPG binds tetrameric Hb at single site, cells its normal equivalent that Hb. This equivalence renders oxygen affinity very sensitive small changes stripped solutions presence nonsaturating concentrations also...

Channel-linked neurotransmitter receptors are membrane-bound heterooligomers made up of distinct, although homologous, subunits. They mediate chemo-electrical signal transduction and its regulation via interconversion between multiple conformations that exhibit distinct pharmacological properties biological activities. The large diversity functional the widely pleiotropic phenotypes, which arise from point mutations in their subunits (or subunit substitutions), interpreted terms an...

Calmodulin plays a vital role in mediating bidirectional synaptic plasticity by activating either calcium/calmodulin-dependent protein kinase II (CaMKII) or phosphatase 2B (PP2B) at different calcium concentrations. We propose an allosteric model for calmodulin activation, which binding to facilitates the transition between low-affinity [tense ( T )] and high-affinity [relaxed R state. The four calcium-binding sites are assumed be nonidentical. is consistent with previously reported...

The properties of human methemoglobin have been investigated under a wide variety conditions to determine its conformation and test for evidence the T state which has proposed by Perutz exist in presence high spin ligands inositol hexaphosphate (IHP). Subunit dissociation was measured as criterion since marked differences tetramer-dimer equilibrium oxyhemoglobin (R state) deoxyhemoglobin (T state). In absence IHP, complexes with both (water, fluoride) or low (azide, cyanide) show extensive...

Studies are reported on the influence of Triton X-100 molecular weight and functional properties acetylcholine receptor. Results presented principally for receptors purified from Torpedo californica marmorata with a limited number observations receptor Electrophorus electricus. In equilibrium dialysis measurements Trito, greatly reduced binding to high affinity sites T. californica, but had only small effect lower affinity. Sedimentation experiments in absence added revealed average apparent...