BOP: A basic phenylalanine‐rich oligo‐peptide located on the surface of glycolate oxidase influences its pI values

Glycolate oxidase (GO) consists of identical subunits and therefore should show one definite pI value, but the isolated GO exhibited a range of pIs. This study investigated the underlying cause of this phenomenon. GO was purified and showed a molecular weight of 40 kDa by SDS‐PAGE. Elution behavior on DEAE‐cellulose chromatography and cellulose acetate membrane electrophoresis indicated that the purified GO was highly basic (pI>10.0). Repeated IEF and cIEF analysis showed that the pI of the purified GO was in the range of 10.0–3.25, either in a smear form or as distinct bands. 2‐DE analysis showed that the 40 kDa subunit of GO displayed variable pIs from 9.6 to 3.65. It was likely that the purified GO was actually a complex consisted of GO and an unknown protein. CE‐SDS, SDS‐cellulose acetate membrane electrophoresis and amino acid compositions indicated that the unknown protein was a highly basic polymer (BP) consisting of basic and phenylalanine‐rich oligo‐peptide (BOP). Many BOPs are located on the surface of the acidic GO via ionic and hydrophobic interactions and formed GO‐BOP complex (GC), resulting in a highly basic GC although GO itself was acidic. This hypothesis was further supported by the facts that anti‐GC serum failed to recognize GO, and GC showed a peak at 257 nm although GO has few phenylalanine residues. Irregular and incomplete disassociation between GO and BOP was observed in IEF and cIEF, resulting in various intermediates with different ratios of GO/BOP, which could be the reason for the range of pIs observed for GO.     

Investigation of the use of density functionals in second‐ and third‐row transition metal dimer calculations

We explore the use of density functionals in calculating the equilibrium distances, dissociation energies, and harmonic vibrational frequencies of the homonuclear diatomics of the second‐row transition metals, platinum, and gold. The outermost s–d interconfigurational energies (ICEs) and the outermost s and d ionization potentials (IPs) were also calculated for the second‐ and third‐row transition metal atoms. Compared with the first‐row transition metal dimer calculations (J Chem Phys 2000, 112, 545–553), the binding energies calculated using the combination of the Becke 1988 exchange and the one‐parameter progressive correlation (BOP) functional and Becke's three‐parameter hybrid (B3LYP) functional are in better agreement with the experiment. However, the pure BOP functional still gives the deep and narrow dissociation potential wells for the electron configurations containing high‐angular‐momentum open‐shell orbitals. Analysis of the s–d ICEs and the s and d IPs suggests that the overestimation may be due to the insufficient long‐range interaction between the outermost s and d orbitals in the exchange functional. The hybrid B3LYP functional seems to partly solve this problem for many systems by the incorporation of the Hartree–Fock exchange integral. However, this still leads to an erroneous energy gap between the configurations of fairly different spin multiplicity, probably because of the unbalance of exchange and correlation contributions. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1995–2009, 2001     

Efficient synthesis of phosphonodepsipeptides derived from norleucine

In the present work, we describe in detail an efficient solution synthesis of norleucine-derived phosphonopeptides mimicking the peptide sequences Nle-Gly(Ala) and Nle-Gly(Ala)-Val. The most efficient strategy involved use of the benzyl group. The synthesis was achieved through BOP-catalysed coupling of the monobenzyl ester of the N-Cbz-protected phosphonate derivative of norleucine with the hydroxyl moieties of derivatised l-lactic or glycolic acid. Subsequently, complete deprotection of the products was achieved in good yields by one-step Pd-catalysed hydrogenolysis. We also prepared the Fmoc-Nle-Ψ[PO(OH)O]-CH₂-COOH synthon and demonstrated that this precursor is a suitable building block for the solid-phase synthesis of cysteine-containing phosphonopeptides.     

Efficient peptide coupling method of conjugated carboxylic acids with methyl ester amino acids hydrochloride. Application to the synthesis of Fa-Met, an important enzymatic substrate

Benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate reagent (BOP) serves as an efficient and versatile coupling reagent for the coupling of conjugated carboxylic acid with methyl ester amino acids hydrochloride allowing the synthesis of various substituted amino acid derivatives in high chemical yields of up to 90%. The usefulness of this method is illustrated in the synthesis of Fa-Met, an important enzymatic substrate.     

Influence of the Tricarbonyl Chromium Complexation of Cyclic Alcohols and of the Planar Chirality on the Kinetic Resolution by Candida Cylindracea Lipase

Tricarbonylchromium complexes of 1-indanol, 1-tetralol, 2-tetralol and the uncomplexed counterparts were kinetically resolved by asymmetric esterification with the Candida cylindracea lipase. We observed a beneficial effect of the tricarbonyl chromium group on the enantioselectivity and we have studied the implication of the relative positions of the tricarbonylchromium group and the alcohol function.