Proline complexes

Isomer shift data, Fe,S4 clusters, 38 20, 50 Isomorphic substitution, 39 179, 186 p-Isonicotinamide complexes, osmium, 37 307 p-lsonicotinamidepoly(proline) complexes, osmium, 37 307 Isonitrile complexes osmium, 37 245 technetium(I), 41 13-14 technetium(II), 41 31 technetium(IIl), 41 45 Isopolymolybdates, 19 239ff 19 265-280 crystallization from aqueous solution, 19 265-269... 

Cotton Effect in Copper-Proline Complexes in the Visible Region 169... 

A crystal structure of the all-tram isomer of [Cr2(gly)4(OH)2] has been reported.1162 Its low temperature magnetic susceptibility has been fitted to both the Van Vleck and modified Van Vleck models. The uncorrected model leads to, uef = 3.80BM with 2/= 8.4 cm-1 1162,1163,1164 with the inclusion of quadratic exchange 2/=7.4 cm-1.1162 Related studies of alanine,1153,1163 valine, phenylalanine, leucine,1163,1149 proline1166,1167 and histidine1168 complexes have appeared. The proline complex is unusual in that it is soluble in methanol and DMSO. Circular dichroism spectra have been measured the X-ray structure shows the complex to be the L-bms(N), L-tram(0) isomer.1166 More complicated dimers of unusual stoichiometry have been reported.1169... 

Various V-alkyl-L-proline complexes of Cu(II) used as additive postcolumn OPA reaction/detection... 

A Derivatives of 1 1 complexes As a result of the chirality of ai-[P2-W17O61]10- (Figure 5) solutions of [ Ce(o i-P2Wi706i)(H20)4 2]14 contain enantiomeric pairs of monomers in equilibrium with the meso dimer. Addition of chiral amino acids to such solutions causes a doubling of the 31P-NMR resonances as a result of diastereomer formation presumably caused by coordination of the amino acid to the rare-earth cation (Sadakane et al., 2001). No splitting was observed when similar experiments were carried out with complexes of the achiral a2 isomer. Formation constants for the two diastereomers of the complexes with L-proline were estimated as 7.3 1.3 and 9.8 1.4 M-1. The corresponding proline complex of achiral [Ce W C i)]7- has a formation constant of 4.5 0.1 M-1 (Sadakane et al., 2002). 

Figure 12. Predicted CD of the p2-S-proline complex (lop) compared with the experimental CD of Compound 9 depicted in Figure 1 (bottom)...

A good example of an investigation into the conformation of coordination of an organic ligand is the work of Singh, Reynolds and Sherry on lanthanide L-proline complexation. The H and paramagnetic shifts and relaxation rates were measured for all H and C atoms of aqueous proline-lanthanide ion solutions at pH 3 for ten lanthanides. It was concluded that while the relaxation data were consistent with an isostructural series, there were inconsistencies in the dipolar shift data, after separation from contact shifts, which could be resolved either by division into two, rather than one, isostructural series, or by invoking biaxial rather than uniaxial symmetry. 

Machesky LM, Cole NB, Moss B, Pollard TD (1994b) Vaccinia virus expresses a novel profilin with a higher affinity for polyphosphoinositides than actin. Biochemistry 33 10815-10824 Mahoney NM, Janmey PA, Almo SC (1997) Structure of the profilin-poly-L-proline complex involved in morphogenesis and cytoskeletal regulation. Nat Struct Biol 4 953-960 Mammoto A, Sasaki T, Asakura T, Hotta I, Imamura H, et al (1998) Interactions of drebrin and gephyrin with profilin. Biochem Biophys Res Commun 243 86-89... 

As was described for HMF in Sect. 2, CMF has likewise been used as a platform for carbon chain extension for the purposes of making higher alkanes. Thus, Silks, et al. describe the direct condensation of CMF with acetone, hydroxy acetone, or dihydroxyacetone in the presence of a zinc-proline complex catalyst [146]. Similarly, Seek recruited CMF as an intermediate in a process that involves various condensations of its derivatives and ultimately hydrotreating to arrive at biofuels [147]. 

Besides nucleobases, the primeval RNA-like polymers may have contained ribose and phosphate entities. Ribose may have been abundant as one of the products of the autocatalytic formose reaction, which was discovered by Butlerov in 1861 [304] and which yields a mixture of pentoses and hexoses from formaldehyde. Although Butlerovs reaction remains the only known autocatalytic reaction that does not require specific catalysts, the importance of this reaction for prebio-logical syntheses has been questioned since the yield of ribose in the product mixture is usually low. Recent studies have shown, however, that the yield of ribose can be selectively enhanced by the presence of phosphate in the reaction medium [305], by UV illumination [16], and by conducting the reaction in the presence of catalytic mineral templates [306]. More recently, it has been demonstrated that the yields of pentoses increase to 60% and those of the ribose proper rise to 20% in the presence of a zinc-proline complex as a catalyst [15]. The Zn world settings may have favoured autocatalytic ribose formation from photosynthesized substrates by providing mineral templates, UV irradiation, and plenty of Zn2-t ions as catalysts. 

Fig, 21. Variation of the experimental normalized peak current with scan rate v for the first (1) and for the second peak (2) in the LSV reduction of Cu(II)-proline complex. Nafion-coated electrode, acetate buffer pH 5,1, cjj/cf = 0.05. Adapted from ref. [85]. 

Addition of nucleophiles to [Cp Ir(T -C2R2)( n C3H5)]+ (R = Me, Ph) occurs at the central allyl carbon to produce the iridacyclobutanes [Cp Ir(ti-C2R2)(CH2CHNuCH2)] (Nu = H, Me, CN, CHMeCOPh).344 xhe chiral prolinate complex [CpIr(OCBut)(02CCHCH2CH2CH2] )l has been prepared as a mixture of diastereomers. ... 

The more active transition metal Zn again differs from Pb as in Sect. 2.1, again preferring a structure having a hydrogen atom covalently attached to the zinc atom. [Zn (Pro-H) H20] (the hydrated zinc-proline counterpart to the lead-proline complex) was assigned as the structure shown in Scheme 7c, which is the structure assigned in Scheme 4 with water attached to flie metal ion [85]. 

Shoeib T, Hopkinson AC, Siu KWM (2001) Collision-induced dissociation of the Ag -l--proline complex fragmentation pathways and reaction mechanisms—a synergy between experiment and theory. J Phys Chem B 105(49) 12399-12409. doi 10.1021/jp012335o... 

More important for UV-MALDI might be IP reductions due to matrix-analyte interactions. Matrix-analyte interactions can be stronger than those between matrix molecules, and there is no a priori reason to expect low two-photon efficiencies for such complexes. Kinsel and colleagues have reported several experimental and theoretical studies of this effect in clusters. In one example, strongly reduced IPs for DHB-proline complexes were found, down to 7eV. ° In addition, fragmentation of some complexes after ionization produced protonated analytes.This is an efficient two-photon process that is probably active for certain matrix-analyte combinations. How often it contributes to MALDI is not yet clear, and this cannot be easily predicted in advance. 

Two main approaches using HPLC are (1) covalent bonding of chiral ligands (which can complex copper (II) ions) to solid supports (such as polystyrene and polyacrylamide) and resolution of amino acids by eluting with a mobile phase containing copper (II) ions (2) introduction of chirality into the mobile phase. Metal ions such as Cu(ll), Zn(n), Co(II), and Mg(II), in conjunction with chiral ligands are added to the mobile phase. Thus, a Cu(n)-L proline complex as the chiral additive can be operated in conventional cation-exchange resin. 

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