Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P39060 (endostatin)
 2,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The synthesis and properties of beta-styrylphosphonic acid (SPA) are reported. The values of the protonation constants of the ligand were determined potentiometrically at different ionic strengths and in the temperature range 0-65 degrees. The enthalpy and entropy of protonation have been calculated by using the van't Hoff isochore. The protonation process is endothermic and is stabilized by a relatively large positive entropy change. The stability constants of the complexes formed between SPA and the bivalent Mg, Ca, Ba, Co, Ni and Pd ions at 25 degrees and ionic strength of 0.12M KNO(3) were also determined. All measurements were carried out in 18% dimethylformamide-water mixture.
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PMID:Metal chelates of phosphonate-containing ligands-II: stability constants of some beta-styrylphosphonic acid metal chelates. 1896 58

L-leucine derived ligand (H(2)L(L-leu)), KOH, and Ni(II) salt in 2:2:1 ratio self-assembled into a rather large (approximately 13 A) supramolecular assembly with the formula [K{Ni(HL(L-leu))(2)}(3)](+) (1). Structural characterization showed three [Ni(HL(L-leu))(2)] units encapsulated K(+) similar to organic crown ethers/cryptand. Substituting Ni(II) with Cu(II) and K(+) with Na(+) in the above reaction resulted in a set of structurally identical assemblies with the general formula [M'{M(HL(L-leu))(2)}(3)](+), where M' is either K(+) or Na(+) and M is either Cu(II) or Ni(II); [Na{Ni(HL(L-leu))(2)}(3)]ClO(4) (2), Na{Ni(HL(L-leu))(2)}(3)]OTf (3), [K{Cu(HL(L-leu))(2)}(3)]ClO(4) (4), [Na{Cu(HL(L-leu))(2)}(3)]ClO(4) (5), [K{Cu(HL(L-leu))(2)}(3)]NO(3) (6). Electrospray Ionization (ESI)-mass spectra of the assemblies in MeOH showed the retention of assemblies in solution. Visible spectroscopic studies showed retention of assembly 1 in N,N-dimethylformamide (DMF) which is stable even after the addition of 5 equiv of [18]-crown-6. The assemblies in 2-6 show various degrees of dissociation to [M(HL(L-leu))(2)] and M', in stronger H-bonding methanol. The dissociation can be reversed upon addition of excess KNO(3)/NaNO(3) salt. Structural characterization of [Cu(HL(L-leu))(2)(MeCN)] (7) along with its transformation to [K{Cu(HL(L-leu))(2)}(3)](+) in the presence of K(+) salt demonstrated that the assembly formation proceeds through an alkali metal ion induced ligand reorientation within the [Cu(HL(L-leu))(2)] units which is further stabilized by six strong H-bonds holding the assembly. Interestingly, visible spectra of 1 and 2 shows that minor structural changes caused by replacing K(+) with Na(+) is sufficient to shift the d-d transition of Ni(II) by approximately 70 nm, thereby providing an indirect way of distinguishing K(+) and Na(+), none of which have spectroscopic signature in the visible range.
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PMID:Sodium and potassium ion directed self-assembled multinuclear assembly of divalent nickel or copper and L-leucine derived ligand. 1974 1