Search results for "Biophysic"
showing 10 items of 3565 documents
Morphology changes induced by intercellular gap junction blocking: A reaction-diffusion mechanism.
2021
Complex anatomical form is regulated in part by endogenous physiological communication between cells; however, the dynamics by which gap junctional (GJ) states across tissues regulate morphology are still poorly understood. We employed a biophysical modeling approach combining different signaling molecules (morphogens) to qualitatively describe the anteroposterior and lateral morphology changes in model multicellular systems due to intercellular GJ blockade. The model is based on two assumptions for blocking-induced patterning: (i) the local concentrations of two small antagonistic morphogens diffusing through the GJs along the axial direction, together with that of an independent, uncouple…
Bioresponsive poly(amidoamine)s designed for intracellular protein delivery.
2013
Poly(amidoamine)s with bioreducible disulfide linkages in the main chain (SS-PAAs) and pH-responsive, negatively charged citraconate groups in the sidechain have been designed for effective intracellular delivery and release of proteins with a net positive charge at neutral pH. Using lysozyme as a cationic model protein these water soluble polymers efficiently self-assemble into nanocomplexes by charge attraction. At pH 5 (the endosomal pH) the amide linkages connecting the citraconate groups in the sidechains of the SS-PAAs are hydrolyzed by intramolecular catalysis, resulting in expulsion of the negative citraconate groups and formation of protonated amine groups, resulting in charge reve…
Cherimolin-1, New Selective Inhibitor of the First Energy-Coupling Site of the NADH:Ubiquinone Oxidoreductase (Complex I)
1997
The mechanism linking electron transport to proton translocation in the NADH:ubiquinone oxidoreductase (complex I of the mitochondrial respiratory chain) is still unclear. Inhibitors acting at different sites of the enzyme are powerful tools to clarify this mechanism. Up to now, a unique inhibitor, the Annonaceous acetogenin rolliniastatin-2, selectively blocks the most internal proton-translocation site. This study introduces cherimolin-1, a new acetogenin that inhibits the complex I with this special mode of action, which is more easily available from the plant material. Moreover, the mode of action of this scarce type of complex I inhibitor is further characterized.
Structure–activity relationship of sphingomyelin analogs with sphingomyelinase from Bacillus cereus
2012
AbstractThe aim of this study was to examine how structural properties of different sphingomyelin (SM) analogs affected their substrate properties with sphingomyelinase (SMase) from Bacillus cereus. Using molecular docking and dynamics simulations (for SMase–SM complex), we then attempted to explain the relationship between SM structure and enzyme activity. With both micellar and monolayer substrates, 3O-methylated SM was found not to be degraded by the SMase. 2N-methylated SM was a substrate, but was degraded at about half the rate of its 2NH–SM control. PhytoPSM was readily hydrolyzed by the enzyme. PSM lacking one methyl in the phosphocholine head group was a good substrate, but PSM lack…
Detoxication of carcinogenic fjord-region diol epoxides of polycyclic aromatic hydrocarbons by glutathione transferase P1-1 variants and glutathione.
1998
AbstractEpidemiological studies suggest that individuals differing in the expression of allelic variants of the human glutathione transferase (GST) Pi gene differ in susceptibility to chemical carcinogens such as polycyclic aromatic hydrocarbons (PAH). This study reports the catalytic efficiencies (kcat/Km) of two naturally occurring variants, GSTP1-1/I-105 and GSTP1-1/V-105, towards a series of fjord-region diol epoxides representing potent biologically active PAH metabolites, and two GSTP1-1 mutants with Ala105 and Trp105 in the active site. The results indicate that individuals who are homozygous for the allele encoding GSTP1-1/V-105 might be more susceptible to PAH carcinogenesis due to…
The purification and properties of nucleoside phosphotransferase from mucosa of chicken intestine
1984
Abstract (1) Nucleoside phosphotransferase (nucleotide:3′-deoxynucleoside 5′-phosphotransferase, EC 2.7.1.77) has been purified from chicken intestine mucosa to apparent homogeneity. The enzyme is represented by a multisubunit protein at different degrees of association. It can dissociate into a compoenent with a marked fall in catalytic activity. (2) The associated forms are similar to the enzyme previously purified from chick embryo as regards: substrate specificity both with respect to nucleoside monophosphate donors and to deoxyribonucleoside acceptors; sigmoidicity in the rate curve with a variable phosphate donor; instability to heat, dilution and lowering of pH; the activating and pr…
Ex Vivo Tracking of Endogenous CO with a Ruthenium(II) Complex.
2017
[EN] A two-photon fluorescent probe based on a ruthenium(II) vinyl complex is capable of selectively detecting carbon monoxide in cells and ex vivo using mice with a subcutaneous air pouch as a model for inflammation. This probe combines highly selective and sensitive ex vivo detection of endogenous CO in a realistic model with facile, inexpensive synthesis, and displays many advantages over the widely used palladium-based systems.
Chemically driven phase separation in black lipid membranes and its coupling to membrane functions
1992
Abstract We analysed the single-channel current fluctuations of gramicidin in bimolecular lipid membranes in order to demonstrate (i) the influence of protein binding to the lateral organisation of a mixed membrane, and (ii) how this couples to the function of the ionophore. Examples of phase separations induced by synthetic polyelectrolytes, as models for peripheral membrane proteins, and specific ligand-receptor interactions are presented and discussed in view of the important lateral order-function relationship in biomembranes.
Crystallization and preliminary X-ray studies of mouse centrin1.
2005
The expression, purification, crystallization and preliminary X-ray diffraction studies of mouse centrin1 are reported. Centrins belong to a family of Ca{sup 2+}-binding EF-hand proteins that play a fundamental role in centrosome duplication and the function of cilia. To shed light on the structure–function relationship of these proteins, mouse centrin1 has been crystallized. The mouse centrin1 has been expressed in Escherichia coli as a GST-centrin fusion protein containing a thrombin protease cleavage site between the fusion partners. Two constructs with different linking-sequence lengths were expressed and purified. Thrombin cleavage yielded functional centrin1 and N-terminally extended …
Differential Enantioselectivity of Murine GlutathioneS-Transferase Isoenzymes in the Glutathione Conjugation ofTrans-3,4-dihydroxy-1,2-oxy- 1,2,3,4-t…
1998
Abstract The kinetics of the glutathione (GSH) conjugation of (+)- and (−)-enantiomers ofanti- as well assyn-3,4-dihydroxy-1,2-oxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (B[c]PDE) catalyzed by murine GSHS-transferase (GST) isoenzymes has been investigated. Murine GSTs exhibited significant differences in their enantioselectivity toward B[c]PDE stereoisomers. For example, while pi class isoenzyme mGSTP1-1 was virtually inactive toward stereoisomers with 1Sconfiguration [(−)-syn-and (+)-anti-B[c]PDE], these stereoisomers were good substrates for alpha class isoenzyme mGSTA1-2. When GST activity was measured as a function of varying B[c]PDE concentration (10–320 μM) at a fixed saturating conce…