calixarenes are a readily available and important class of macrocycles in supramolecularchemistry. calixarenes have generated considerable interest due to their basket shaped structureand as useful building blocks to synthesize selective receptors for the guest species, notably alkali,alkaline earth, lanthanide and transition metal cations. in this work studied on the complexingproperties of a ...

We studied the effect of ions on the ability of purified human urinary kallikrein to cleave its natural substrate (kininogen) as well as two synthetic substrates, tosylarginine [3H]methyl ester and Pro-Phe-Arg-[3H]benzylamide. The kininogenase activity of kallikrein is markedly dependent upon the concentration of cations in vitro. Kininogenase activity is very low when measured in a low electro...

A collection of organic cations has been used to probe the gross structural features of the ionic diffusion pathway in a K+-selective channel from sarcoplasmic reticulum (SR). Channels were incorporated into planar phospholipid bilayer membranes, and single-channel currents were measured in the presence of ammonium-derived cations in the aqueous phases. Small monovalent organic cations are able...

Transient receptor potential vanilloid type 1 (TRPV1) channel responds to a wide spectrum of physical and chemical stimuli. In doing so, it serves as a polymodal cellular sensor for temperature change and pain. Many chemicals are known to strongly potentiate TRPV1 activation, though how this is achieved remains unclear. In this study we investigated the molecular mechanism underlying the gating...

Biological membrane fusion employs divalent cations as protein cofactors or as signaling ligands. For example, Mg2+ is a cofactor for the N-ethylmaleimide-sensitive factor (NSF) ATPase, and the Ca2+ signal from neuronal membrane depolarization is required for synaptotagmin activation. Divalent cations also regulate liposome fusion, but the role of such ion interactions with lipid bilayers in Ra...

TRPV6 (CaT1/ECaC2), a highly Ca(2+)-selective member of the TRP superfamily of cation channels, becomes permeable to monovalent cations in the absence of extracellular divalent cations. The monovalent currents display characteristic voltage-dependent gating and almost absolute inward rectification. Here, we show that these two features are dependent on the voltage-dependent block/unblock of the...

Synaptotagmins are synaptic vesicle-associated, phospholipid-binding proteins most commonly associated with Ca 1 2 -dependent exocytotic and Ca 1 2 independent endocytotic events. Synaptotagmin III is a 63.2-kD member of the synaptotagmin homology group; one of its characteristic properties is the ability to bind divalent cations and accessory proteins promiscuously. In the cytosolic portion of...

Synaptotagmins are synaptic vesicle-associated, phospholipid-binding proteins most commonly associated with Ca(+2)-dependent exocytotic and Ca(+2)- independent endocytotic events. Synaptotagmin III is a 63.2-kD member of the synaptotagmin homology group; one of its characteristic properties is the ability to bind divalent cations and accessory proteins promiscuously. In the cytosolic portion of...

We report coupled cluster, MP2 and DFT data on the relative energy geometry of α-sheet β-strand conformations model peptides. show that ionic effects have a strong effect balance through formation multiple cation-oxygen contacts in form. Such are markedly dependent both sequence ion: two peptides considered favour presence cations, whereas third, non-polar one favours same conditions.