Depletion of phosphatidyl-glycerol head-group induces changes in oxygen evolution and protein secondary struc-tures of photosystem Ⅱ

The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and structural aspects of photosystem Ⅱ (PS Ⅱ) through enzymatic approach. It was shown that the depletion of PG by treatment of phospholipase C (PLC) on PS Ⅱ particles caused the inhibition of oxygen evolving activity in PS Ⅱ. This effect also gave rise to changes in the protein secondary structures of PS Ⅱ, that is, an increase in a-helical conformation which is compensated by the loss of p-strand structures. It revealed that the head-group of PG molecules plays an important structural role in the maintenance of normal structure of PS Ⅱ proteins, which is required to maintain the appropriate physiological activity of the PS Ⅱ complex such as the oxygen evolving activity. It is suggested that there most probably exist hydrogen-bonding interactions between PG molecules and PS Ⅱ proteins.     

Molecular recognition study on a supramolecular system (ⅩⅤ)──Molecular recognition of aliphatic alcohols by some phenyl-selenium modified β-cyclodextrins

The spectrophotometric titrations have been performed at 298.15 K in buffered aqueous solution (pH 7.20) to give the stability constants (logK-s) for the supramolecular system formed by mono-[6-(phenylseleno)-6-deoxy]-β-cyclodextrin (2), mono-[6-(p-tolylseleno)-6-deoxy]-β-cyclodextrin (3), mono-[6-(o-tolylseleno)-6-deoxy]-β-cyclodextrin (4), mono-[6-(m-tolylseleno)-6-deoxy]-β-cyclodextrin (5) with a series of aliphatic alcohols. The results were compared with the data reported for the parent β-cyclodextrin. The molecular binding ability and selectivity for aliphatic alcohols of modified β-cyclodextrins (2_5) were discussed from the viewpoints of the induced-fit and geometrical complement. The results obtained indicate that the phenylseleno moiety of β-cyclodextrin derivatives (2_5) as a probe for spectrometry can enhance not only the molecular binding ability but also the molecular recognition ability.     

Synthesis,thermal decomposition and crystal structure of copper (Ⅱ)α,β-unsaturated carboxylate with urea

A detailed synthesis is described for binuclear cage ternary complexes Cu2A4 [(NH2)2CO]2, where A = CH2 =CH-COO and CH2 =C(CH3)-COO- . Elemental analysis and thermal analysis have been investigated. The molecular structure of Cu2 (CH2 = CH-COO)4[(NH2)2CO]2 was determined by single crystal X-ray diffraction. The material forms blue crystal with tetragronal symmetry, space group P42/n, a = b = 1.239 35(6) nm, c = 1.398 05 (16) nm, Z = 4. There exists a magnetic exchange interaction between the two paramagnetic Cu atoms. The Cu-Cu bond length is 0.260 94 nm.     

Syntheses, characterization, crystal structure and magnetic properties of copper(Ⅱ)α, β-unsaturated carboxylate complexes with trimethyl phosphate

Two ternary complexes Cu2A4[OP(OCH₃)₃]₂ (A represents CH₂== CH—COO- and CH₂== C(CH₃)—COO-) have been synthesized, and elemental analyses, IR, ESR, electronic reflectance spectra and magnetic studies were carried out. The single crystal X-ray diffraction shows that Cu₂[CH₂== C(CH₃)—COO]₄[OP(OCH₃)₃]₂ is triclinic, with space group P1, a = 1.05128(13), b = 1.7559(5), c = 1.94479(3) nm, α = 91.263(14)°, β = 102.559(6)°, γ = 106.339(13)°, Z = 4 and R = 0.0668. Two copper(Ⅱ) atoms are bridged by four a -methacrylate groups, and each copper(Ⅱ) atom is coordinated with a trimethyl phosphate molecule in the axial position, forming a distorted square pyramidal configuration. The symmetric center is between the two copper(Ⅱ) atoms, and the Cu-Cu bond distance is 0.26098(6) nm. The Cu-Cu distance and magnetic studies suggest that there exist antiferromagnetic interactions between the two copper(Ⅱ) atoms.