Binding Reaction (binding + reaction)

Distribution by Scientific Domains

Selected Abstracts

Interactions of cyclosporines with lipid membranes as studied by solid-state nuclear magnetic resonance spectroscopy and high-sensitivity titration calorimetry

Uwe Schote
Abstract Cyclosporin A (CyA) interacts with lipid membranes. Binding reaction and membrane location of CyA and analogs were examined with 2H-NMR, high-sensitivity isothermal titration calorimetry (ITC), and CD spectroscopy. Effects of CyA and charged analogs on the phosphocholine head group and on the membrane interior were investigated using selectively deuterated phospholipids. Incorporation of cyclosporin generated small disordering of the lipid acyl chains. Binding of CyA and neutral and positively charged analogs to lipid membranes showed endothermic heats of reaction between +,5.9 and +,11.3 kcal/mol, whereas enthalpy of binding was close to zero for the negatively charged derivative. Binding constants of cyclosporines to liposomal membranes were in the range of KP,=,1650,5560 M,,1 depending on the cholesterol content. 2H-NMR provides evidence that CyA is essentially located in the interior of the bilayer membrane. For the charged analogs an additional interaction occurs at the head group level, placing the polar groups of these CyA analogs in the vicinity of the phosphocholine dipoles. The association of CyA and its analogs is accompanied by a positive enthalpy change, which is overcompensated by positive entropy changes. Binding of CyA to lipid membranes thus follows the classical hydrophobic effect, which is in contrast to many other peptide-lipid binding reactions. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91: 856,867, 2002 [source]

Molecular Interaction between a Gadolinium,Polyoxometalate and Human Serum Albumin

Li Zheng
Abstract Polyoxometalates (POMs) show promising antibacterial, antiviral (particularly anti-HIV), antitumor, and anticancer activities, but the mechanism of these potential therapeutic effects remains to be elucidated at the molecular level. The interaction between the Gd-containing tungstosilicate [Gd(,2 -SiW11O39)2]13, and human serum albumin (HSA) was studied by several techniques. Fluorescence spectroscopy showed an energy transfer between the single tryptophan residue of HSA and the POM. Circular dichroism led to the conclusion that the POM significantly altered the secondary structure of HSA. Isothermal titration calorimetry revealed an enthalpy-driven binding reaction between HSA and the POM, resulting in the formation of a 1:1 complex.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Antisense RNA regulation of the par post-segregational killing system: structural analysis and mechanism of binding of the antisense RNA, RNAII and its target, RNAI

Tony J. Greenfield
The par stability determinant of the Enterococcus faecalis plasmid pAD1 is the first antisense RNA regulated post-segregational killing system (PSK) identified in a Gram-positive organism. Par encodes two small, convergently transcribed RNAs, designated RNAI and RNAII, which are the toxin and antitoxin of the par PSK system respectively. RNAI encodes an open reading frame for a 33 amino acid toxin called Fst. Expression of fst is regulated post-transcriptionally by RNAII. RNAII interacts with RNAI by a unique antisense RNA mechanism involving binding at the 5, and 3, ends of both RNAs. Par RNA interaction requires a complementary transcriptional terminator stem-loop and a set of direct repeat sequences, DRa and DRb, located at the 5, end of both RNAs. The secondary structures of RNAI, RNAII and the RNAI,RNAII complex were analysed by partial digestion with Pb(II) and ribonucleases. Probing data for RNAI and RNAII are consistent with previously reported computer generated models, and also confirm that complementary direct repeat and terminator sequences are involved in the formation of the RNAI,RNAII complex. Mutant par RNAs were used to show that the binding reaction occurs in at least two steps. The first step is the formation of an initial kissing interaction between the transcriptional terminator stem-loops of both RNAs. The subsequent step(s) involves an initial pairing of the complementary direct repeat sequences followed by complete hybridization of the 5, nucleotides to stabilize the RNAI,RNAII complex. [source]

Direct Evidence of Covalent Immobilisation of Microperoxidase-11 on Plasma Polymer Surfaces

Yongbai Yin
Abstract The question of whether immobilised proteins are bound covalently on plasma activated or deposited polymers has been a challenge for almost 30 years, as there has been no directly evidence to conclude unambiguously. In this paper, we report evidence that a chemical binding reaction occurred during immobilisation of microperoxidase-11 (MP-11) proteins on plasma polymer surfaces. Untreated polymer surfaces were not resistant to detergent cleaning and did not show any increase of S 2p component after protein immobilisation, whilst all plasma-deposited surfaces showed large amounts of immobilised MP-11 proteins after detergent cleaning. We conclude that the MP-11 protein had a chemical binding reaction thorough its cysteine residues with the plasma polymer surfaces. [source]

Selective solid-phase isolation of methionine-containing peptides and subsequent matrix-assisted laser desorption/ionisation mass spectrometric detection of methionine- and of methionine-sulfoxide-containing peptides

Tom Grunert
Methionine residues and the oxidised forms in proteins are becoming more and more important in view of their biological function. In particular, methionine sulfoxide seems to have a regulatory function. This paper presents a fast strategy for simultaneous determination of methionine- and methionine-sulfoxide-containing peptides, involving application of methionine-specific solid-phase reagent chemistry combined with matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). In the first step, methionine-containing peptides are covalently bound as sulfonium salts to glass beads, whereas methionine-sulfoxide-containing peptides and other methionine-free peptides are not bound and are washed out. The wash solution is used for MALDI-MS analysis to determine the molecular masses of these peptides and to perform, if necessary, seamless post-source decay (PSD) fragment ion analysis. Methionine-sulfoxide-containing peptides can be identified due to the characteristic metastable loss of methanesulfenic acid from the protonated molecules. In the second step, the bound peptides are cleaved from the matrix of the beads by addition of 2-mercaptoethanol at pH,8.5,8.8. The resulting peptides, mainly methionine-containing peptides, are analysed in a straightforward manner by MALDI-MS and seamless PSD. The strategy allows the fast identification of methionine- and methionine-sulfoxide-containing peptides even in complex tryptic digests, as demonstrated here for the glycoprotein antithrombin. These results show that sometimes methionine-containing tryptic peptides are not detected due to steric restrictions (e.g. glycosylation near the methionine residue) on the binding reaction, and that, on the other hand, some methionine-free peptides can be quite strongly bound non-covalently to the matrix of the beads. The latter observation indicates the necessity of seamless PSD fragment ion analysis for unambiguous identification. Furthermore, there are indications that oxidation of some methionine residues occurred to a minor extent during the solid-phase isolation steps. Copyright © 2003 John Wiley & Sons, Ltd. [source]

The Development of the Metanephric Kidney in the Pig

H. Bragulla
Aims:, The metanephric kidneys of the pig are used as xenotransplants in human medicine. In order for transplants to fit within the host organisms, the subcapsular blastema and blood vessels are crucial for the development of new nephrons to sustain the organ functions. The aim of this study is to obtain data concerning the post-natal development of metanephric nephrons in the porcine kidney. Materials and Methods:, The metanephric kidneys of six porcine fetuses with a crown-rump length ranging from 40 mm to 220 mm of eight piglets aged between 6 to 10 weeks and of three adult pigs were studied. Eight lectins as well as anti-actin and anti-myosin antibodies were used for lectin- and immunohistochemistry to study the subcapsular metanephric blastema, to visualize the blood-urine barrier in the nephrons and collecting tubules, and to study the blood vessels in both the renal cortex and marrow. Results and Conclusions:, A subcapsular metanephric blastema was still present in the kidney of 10-week-old piglets. Dense condensation of mesenchymal cells surrounded the terminal branches of the collecting ducts and showed first signs of mesenchymal-epithelial transformation. Characteristic comma-shaped and s-shaped bodies were found in and underneath the subcapsular blastema. In the fibrous renal capsule of six-week-old piglets, a first faint binding reaction of anti-actin was visible and intensified in the fibrous renal capsule in ten-week-old piglets and in adult pigs. In addition, the smooth-muscle layers of the blood vessels were stained by the anti-actin and anti-myosin antibodies. The lectins showed various affinities to the endothelium of blood vessels and to the epithelial cells lining of the capsules of the metanephric renal corpuscles, the various parts of the renal tubules, as well as the collecting tubules and the renal pelvis. The affinity of the epithelial cells to a specific lectin varies in neighbouring cells, indicating different cell activities or cell cycles. [source]

Structural and thermodynamic insights into the binding mode of five novel inhibitors of lumazine synthase from Mycobacterium tuberculosis

FEBS JOURNAL, Issue 20 2006
Ekaterina Morgunova
Recently published genomic investigations of the human pathogen Mycobacterium tuberculosis have revealed that genes coding the proteins involved in riboflavin biosynthesis are essential for the growth of the organism. Because the enzymes involved in cofactor biosynthesis pathways are not present in humans, they appear to be promising candidates for the development of therapeutic drugs. The substituted purinetrione compounds have demonstrated high affinity and specificity to lumazine synthase, which catalyzes the penultimate step of riboflavin biosynthesis in bacteria and plants. The structure of M. tuberculosis lumazine synthase in complex with five different inhibitor compounds is presented, together with studies of the binding reactions by isothermal titration calorimetry. The inhibitors showed the association constants in the micromolar range. The analysis of the structures demonstrated the specific features of the binding of different inhibitors. The comparison of the structures and binding modes of five different inhibitors allows us to propose the ribitylpurinetrione compounds with C4,C5 alkylphosphate chains as most promising leads for further development of therapeutic drugs against M. tuberculosis. [source]

Nucleic Acid Biosensor for Detection of Human Immunodeficiency Virus Using Aquabis(1,10-phenanthroline)copper(II) Perchlorate as Electrochemical Indicator

Shu-Yan NIU
Abstract The electrochemical behavior of aquabis(1,10-phenanthroline)copper(II) perchlorate [Cu(H2O)(phen)2]·2ClO4, where phen=1,10-phenanthroline, on binding to DNA at a glassy carbon electrode (GCE) and in solution, was described. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that [Cu(H2O)(phen)2]2+ had excellent electrochemical activity on the GCE with a couple of quasi-reversible redox peaks. The interaction mode between [Cu(H2O)(phen)2]2+ and double-strand DNA (dsDNA) was identified to be intercalative binding. An electrochemical DNA biosensor was developed with covalent immobilization of human immunodeficiency virus (HIV) probe for single-strand DNA (ssDNA) on the modified GCE. Numerous factors affecting the probe immobilization, target hybridization, and indicator binding reactions were optimized to maximize the sensitivity and speed of the assay. With this approach, a sequence of the HIV could be quantified over the range from 7.8×10,9 to 3.1×10,7 mol·L,1 with a linear correlation of ,=0.9987 and a detection limit of 1.3×10,9 mol·L,1. [source]