Crystal structures of seven mixed-valence gold compounds of the form [( P)Au][Au ] ( = -butyl or isopropyl, = S or Se, and = Cl or Br).

During our studies of the oxidation of gold(I) complexes of tri-alkyl-phosphane chalcogenides, general formula PAu, ( = -butyl or isopropyl, = S or Se, = Cl or Br) with PhICl or elemental bromine, we have isolated a set of seven mixed-valence by-products, the bis-(tri-alkyl-phosphane chalcogenido)gold(I) tetra-halogenidoaurates(III) [( P)Au][Au ]. These corres-pond to the addition of one halogen atom per gold atom of the Au precursor. Com-pound , bis-(triiso-propyl-phosphane sulfide)-gold(I) tetra-chlorido-aur-ate(III), [Au(CHPS)][AuCl] or [( PrPS)Au][AuCl], crystallizes in space group 2/ with = 4; the gold(I) atoms of the two cations lie on twofold rotation axes, and the gold(III) atoms of the two anions lie on inversion centres.

(2,4)-5-Fluoroleucine, (2,4)-5-Fluoroleucine, and 5,5'-Difluoroleucine in PpiB: Protein Production, F NMR, and Ligand Sensing Enhanced by the γ-Gauche Effect.

Global substitution of leucine for analogues containing CHF instead of methyl groups delivers proteins with multiple sites for monitoring by F nuclear magnetic resonance (NMR) spectroscopy. The 19 kDa peptidyl-prolyl isomerase B (PpiB) was prepared with uniform high-level substitution of leucine by (2,4)-5-fluoroleucine, (2,4)-5-fluoroleucine, or 5,5'-difluoroleucine. The stability of the samples toward thermal denaturation was little altered compared to the wild-type protein.

Conformational Preferences of the Non-Canonical Amino Acids (2,4)-5-Fluoroleucine, (2,4)-5-Fluoroleucine, and 5,5'-Difluoroleucine in a Protein.

Proteins produced with leucine analogues, where CHF groups substitute specific methyl groups, can readily be probed by F NMR spectroscopy. As CF and CH groups are similar in hydrophobicity and size, fluorinated leucines are expected to cause minimal structural perturbation, but the impact of fluorine on the rotational freedom of CHF groups is unclear. We present high-resolution crystal structures of peptidyl-prolyl - isomerase B (PpiB) prepared with uniform high-level substitution of leucine by (2,4)-5-fluoroleucine, (2,4)-5-fluoroleucine, or 5,5'-difluoroleucine.

Crystal structures of fourteen halochalcogenylphos-pho-nium tetra-halogenidoaurates(III).

The structures of fourteen halochalcogenyl-phospho-nium tetra-halogen-ido-aurates(III), phosphane chalcogenide derivatives with general formula [ P][Au ] ( = -butyl; = isopropyl; = 0 to 3; = S or Se; = Cl or Br) are presented. The eight possible chlorido derivatives are: , = 3, = S; , = 2, = S; , = 1, = S; , = 0, = S; , = 3, = Se; , = 2, = Se; , = 1, = Se; and , = 0, = Se, and the corresponding bromido derivatives are - in the same order. Structures were obtained for all compounds except for the tri--butyl derivatives and .

Crystal structures of ten phosphane chalcogenide complexes of gold(III) chloride and bromide.

The structures of ten phosphane chalcogenide complexes of gold(III) halides, with general formula PAu ( = -butyl; = -propyl; = 0 to 3; = S or Se; = Cl or Br) are presented. The eight possible chlorido derivatives are: , = 3, = S; , = 2, = S; , = 1, = S; , = 0, = S; , = 3, = Se; , = 2, = Se; , = 1, = Se; and , = 0, = Se, and the corresponding bromido derivatives are - in the same order. Structures were obtained for , (and a second polymorph ), (and its deutero-chloro-form monosolvate ), (as its di-chloro-methane monosolvate), , (as its deutero-chloro-form monosolvate , in which the solvent mol-ecule is disordered over two positions), , , and .