Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reaction of several plasmin derivatives with alpha 2-macroglobulin (alpha 2M) has been investigated. Titration experiments measuring conformational changes in alpha 2M, changes in the number of sulfhydryl groups available for titration with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), and changes in the ability of alpha 2M to protect bound plasmin from inhibition by soybean trypsin inhibitor all suggested that between 1.3 and 1.5 mol of plasmin was bound per mole of inhibitor. Under experimental conditions where [plasmin] greater than [alpha 2M], the conformational change occurring in the inhibitor and thiol group appearance displayed biphasic kinetics. Examination of the extent of subunit cleavage by plasmin revealed that the rapid phase was associated with cleavage of approximately two to three of the four alpha 2M subunits, while cleavage of the remaining subunits occurred during the slow phase of the reaction. Binary (1:1) alpha 2M-plasmin complexes were prepared by reacting a large excess of alpha 2M with plasmin and purifying the resultant complex by immunoaffinity chromatography using a monoclonal antibody specific for a neoantigen on alpha 2M that is generated when the inhibitor reacts with proteases or with methylamine. Characterization of the purified complex revealed that two of the four subunits were cleaved, and the conformational change, measured by alterations in the fluorescence of 6-(p-toluidino)-2-naphthalenesulfonate (TNS), was approximately 50% of that measured for a 2:1 complex. Thus it appears that proteolysis and conformational alterations associated with the binding of 1 mol of plasmin to alpha 2M are limited to one of two functional units in the molecule.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of the reaction of plasmin with alpha 2-macroglobulin: effect of antifibrinolytic agents. 245 May 63

Human brain S100b (beta beta) protein was purified using zinc-dependent affinity chromatography on phenyl-Sepharose. The calcium- and zinc-binding properties of the protein were studied by flow dialysis technique and the protein conformation both in the metal-free form and in the presence of Ca2+ or Zn2+ was investigated with ultraviolet spectroscopy, sulfhydryl reactivity and interaction with a hydrophobic fluorescence probe 6-(p-toluidino)naphthalene-2-sulfonic acid (TNS). Flow dialysis measurements of Ca2+ binding to human brain S100b (beta beta) protein revealed six Ca2+-binding sites which we assumed to represent three for each beta monomer, characterized by the macroscopic association constants K1 = 0.44 X 10(5) M-1; K2 = 0.1 X 10(5) M-1 and K3 = 0.08 X 10(5) M-1. In the presence of 120 mM KCl, the affinity of the protein for calcium is drastically reduced. Zinc-binding studies on human S100b protein showed that the protein bound two zinc ions per beta monomer, with macroscopic constants K1 = 4.47 X 10(7) M-1 and K2 = 0.1 X 10(7) M-1. Most of the Zn2+-induced conformational changes occurred after the binding of two zinc ions per mole of S100b protein. These results differ significantly from those for bovine protein and cast doubt on the conservation of the S100 structure during evolution. When calcium binding was studied in the presence of zinc, we noted an increase in the affinity of the protein for calcium, K1 = 4.4 X 10(5) M-1; K2 = 0.57 X 10(5) M-1; K3 = 0.023 X 10(5) M-1. These results indicated that the Ca2+- and Zn2+-binding sites on S100b protein are different and suggest that Zn2+ may regulate Ca2+ binding by increasing the affinity of the protein for calcium.
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PMID:Purification, characterization and ion binding properties of human brain S100b protein. 648 34

Small unilamellar vesicles (SUVs) formed from a mixture of dimyristoylphosphatidylcholine (zwitterionic lipid with bulkier headgroup) and dimyristoylphosphatidylglycerol (anionic lipid with relatively smaller headgroup) allows better modulation of the physical properties of lipid bilayers compared to SUVs formed by a single type of lipid, providing us with a better model system to study the effect of membrane parameters on the partitioning of small molecules. Membrane parameter like packing of the vesicles is more pronounced in the gel phase and hence the study was carried out in the gel phase. Mixed vesicles formed from DMPG and DMPC with the mole percent ratio of 100:0, 90:10 and 80:20 were used for this study. As examples of polar solutes, piroxicam and meloxicam, two Non Steroidal Anti-inflammatory Drugs (NSAIDs) were chosen. The pH was adjusted to 2.8 in order to eliminate the presence of anionic forms of the drugs that would not approach the vesicles containing negatively charged DMPG (50% deprotonated at pH 2.8). Surface potential measured by using TNS (2,6-p-toluidinonaphthalene sulfonate, sodium salt) as surface charge sensitive probe showed no significant changes in the surface electrostatics in increasing DMPC content from 0 to 20%. Transmission electron microscopy (TEM) was used to characterize SUVs of different composition at pH 2.8. The average diameter of the mixed vesicles was found to be smaller than that formed by DMPG and DMPC alone. Partition coefficient (K(P)) of piroxicam and meloxicam was measured using intrinsic fluorescence of these molecules. K(P) value of piroxicam decreases with increase in DMPC content whereas it increases with DMPC content in case of meloxicam. This anomalous behavior of partitioning is unexpected since there was no significant change in surface pH of the vesicles and has been explained in terms of lipid packing and water penetration in the lipid bilayer.
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PMID:Interaction of piroxicam and meloxicam with DMPG/DMPC mixed vesicles: anomalous partitioning behavior. 1701 May 2