Monitoring of heparin and its low-molecular-weight analogs by silicon field effect.

Heparin is a highly sulfated glycosaminoglycan that is used as an important clinical anticoagulant. Monitoring and control of the heparin level in a patient's blood during and after surgery is essential, but current clinical methods are limited to indirect and off-line assays. We have developed a silicon field-effect sensor for direct detection of heparin by its intrinsic negative charge.

Immobilized N-alkylated polyethylenimine avidly kills bacteria by rupturing cell membranes with no resistance developed.

Several critical mechanistic and phenomenological aspects of the microbicidal surface coatings based on immobilized hydrophobic polycations, previously developed by us, are addressed. Using Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria, remarkable bactericidal action (up to a 10(9)-fold reduction in live bacteria count in the surface-exposed solution and a 100% inactivation of the surface-adhered bacteria) of an amino-glass slide covalently derivatized with N-hexyl,methyl-polyethylenimine (PEI) is found to be due to rupturing bacterial cell membranes by the polymeric chains. The bacteria fail to develop noticeable resistance to this lethal action over the course of many successive generations.

Conjugate of palladium(II) complex and beta-cyclodextrin acts as a biomimetic peptidase.

We combined the newly discovered ability of [Pd(H2O)4]2+ to residue-selectively hydrolyze X-Pro bonds in peptides at 6 View Article and Find Full Text PDF

Transition-metal complexes as enzyme-like reagents for protein cleavage: complex cis-[Pt(en)(H2O)2]2+ as a new methionine-specific protease.

Complex cis-[Pt(en)(H(2)O)(2)](2+) promotes selective hydrolytic cleavage of two proteins, horse cytochrome c and bovine beta-casein. The cleavage is completed in 24 h under relatively mild conditions, at about pH 2.5, and a temperature as low as 40 degrees C.

Combined use of platinum(II) complexes and palladium(II) complexes for selective cleavage of peptides and proteins.

This study shows, for the first time, the advantages of combining two transition-metal complexes as selective proteolytic reagents. In this procedure, cis-[Pt(en)(H(2)O)(2)](2+) is followed by [Pd(H(2)O)(4)](2+). In the peptide AcAla-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala, the Pt(II) reagent cleaves the Met6-Ala7 peptide bond, whereas the Pd(II) reagent cleaves the Gly4-Gly5 bond.

Palladium(II) complex as a sequence-specific peptidase: hydrolytic cleavage under mild conditions of X-Pro peptide bonds in X-Pro-Met and X-Pro-His segments.

The X-Pro peptide bond (in which X represents any amino acid residue) in peptides and proteins is resistant to cleavage by most proteolytic enzymes. We show that [Pd(H(2)O)(4)](2+) ion can selectively hydrolyze this tertiary peptide bond within the X-Pro-Met and X-Pro-His sequence segments. The hydrolysis requires an equimolar amount of the Pd(II) reagent and occurs under mild conditions-at temperature as low as 20 degrees C (with half-life of 1.

Interplay of terminal amino group and coordinating side chains in directing regioselective cleavage of natural peptides and proteins with palladium(II) complexes.

Palladium(II) ions anchored to side chains of histidine and methionine residues in peptides and proteins in weakly acidic aqueous solutions promote hydrolytic cleavage of proximate amide bonds in the backbone. In this study, we determine how attachment of Pd(II) ions to histidine and methionine anchors and also to the terminal amino group in six natural peptides (chains A and B of insulin, segment 11-14 of angiotensinogen, pentagastrin, angiotensin II, and segment 3-8 of angiotensin II) and two proteins (ubiquitin and cytochrome c) affects regioselectivity and rate of backbone cleavage. These Pd(II)-promoted reactions follow a clear pattern of regioselectivity, directed by the anchoring side chains.

Palladium(II) complexes, as synthetic peptidases, regioselectively cleave the second peptide bond "upstream" from methionine and histidine side chains.

Palladium(II) complexes promote hydrolysis of natural and synthetic oligopeptides with unprecedented regioselectivity; the only cleavage site is the second peptide bond upstream from a methionine or a histidine side chain, that is, the bond involving the amino group of the residue that precedes this side chain. We investigate this regioselectivity with four N-acetylated peptides as substrates: neurotransmitter methionine enkephalin (Ac-Tyr-Gly-Gly-Phe-Met) and synthetic peptides termed Met-peptide (Ac-Ala-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala), His-peptide (Ac-Val-Lys-Gly-Gly-His-Ala-Lys-Tyr-Gly-Gly-Met(OX)-Ala-Ala-Arg-Ala), in which a Met is oxidized to sulfone, and HisMet-peptide (Ac-Val-Lys-Gly-Gly-His-Ala-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala). While maintaining protein-like properties, these substrates are suitable for quantitative study since their coordination to Pd(II) ion can be determined (by NMR spectroscopy), and the cleavage fragments can be separated (by HPLC methods) and identified (by MALDI mass spectrometry).