Search

The oligomeric structure of native and low ionic strength-dissociated human erythrocyte tripeptidyl peptidase II (TPP-II) have been investigated by PAGE (without SDS) and transmission electron microscopy. The native TPP-II complex has a very high molecular mass (>10 6 ) and has a ‘double bow’ or short double helical conformation, 50 nm in length and 20 nm wide. This complex dissociates into a range of smaller oligomers upon dialysis against a dilute Tris-HCl buffer, with an M r 270,000 dimer having some tendency to predominate during short (1 to 4 h) dialysis times. Small 2-dimensional arrays of the dissociation products have been produced using the negative staining-carbon film technique when polythylene glycol ( M r 10,000) is included, within which the M r 270,000 dimer of TPP-II appears to be the repeating unit.

A recombinant truncated form (delta1-102/delta428-452) of the non-heme iron-dependent metalloenzyme human phenylalanine hydroxylase (hPAH, phenylalanine 4-monooxygenase; EC 1.14.16.1) was expressed in E. coli, purified to homogeneity as a homodimer (70 kDa) and crystallized using the hanging drop vapour diffusion method. The crystals are orthorhombic, space group C222 with cell dimensions of a = 66.6 A, b = 108.4 A, c = 125.7 A. The calculated packing parameter (Vm) is 3.24 A3/Da with four 2-fold symmetric dimers (or eight momomers) in the unit cell. Data have been collected to 2.0 A resolution.

Columns packed with 0.3–0.4% OV-225 on Chromosorb surface modified wit high-molecular-weight polythylene glycol have been developed for the gas chromatographic analysis of methylated sugar derivatives. These columns provided a better separation of O-acetyl-O-methylmannitols and -galactitols than those usually employed (packed with 3% ECNSS-M or 3% OV-225) and an exceptionally good resolution of O-trimethylsilyl(TMS)-O-methylalditols. Methylated derivatives of glucosamine could be chromatographed well both in the form of N,O-acetylgluco- saminitols and as the corresponding N-acetyl-O-TMS derivatives. Short retention times make it possible to perform analyses rapidly and at temperatures 40–50° lower than the upper operation limit of the packing ( ca . 250°). Column bleeding is negligible, thus ensuring that the retention parameters are constant for long-term functioning of the column.