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Raman spectra have been demonstrated repeatedly to be a very valuable tool for the analysis of new carbon phases such as fullerenes and single wall carbon nanotubes (SWCNTs). Recently it was demonstrated from TEM analysis that C 60 can be encapsulated into SWCNTs. The structures have been given the name ‘peapods’. The concentration of the encapsulated ‘peas’ and the bonding structure in the tube are still unknown but under heavy discussion. From experience with C 60 and SWCNTs, Raman spectroscopy is expected to be a key technique for the analysis of such structures. In our experiments, we found two modes in the region of the pentagonal pinch mode of C 60 . The resonance behavior for these two modes and their temperature dependence is shown in this paper.

Propaquizafop absorption, translocation, metabolism, and effects on acetyl-CoA carboxylase (ACCase) isoforms were examined in chickpea (Cicer arientinum L.). Maximum foliar absorption of propaquizafop, approximately 35% of recovered herbicide, occurred 48 h after treatment. Of the absorbed propaquizafop, approximately 30% was rapidly metabolized to the acid form followed by a slow conversion of the acid to a polar metabolite. Approximately 4% of foliar-applied [14C]propaquizafop was translocated from the treated leaflets within 72 h after application. Chloroplast stromal and cytosolic fractions were isolated from chickpea leaves. Proteins from both fractions were separated by SDS–PAGE and probed with avidin–alkaline phosphatase to detect biotinylated polypeptides. The cytosolic fraction contained a multifunctional ACCase as indicated by the presence of a biotinylated polypeptide of 200 kDa. The chloroplast stromal fraction contained the 36-kDa biotinylated subunit of the multi-subunit ACCase and a 200-kDa biotinylated protein which suggested the presence of a plastid-localized multifunctional ACCase. Pretreating isolated chloroplasts with thermolysin prior to lysis did not reduce the presence of the 200-kDa biotinylated protein. ACCase activity in both cytosolic and stromal fractions exhibited a high level of tolerance to propaquizafop acid and other graminicides. Total ACCase activity in the chickpea chloroplast stroma fraction appears to be composed of activities contributed by both multisubunit and multifunctional ACCases.

The radial breathing mode around 190 cm -1 was investigated for excitation with 30 different laser lines. It exhibits an oscillatory behaviour with respect to excitation energy. This oscillations could be traced back to the periodicity of the van Hove singularities. Using the first and the second spectral moments parameters characterizing a diameter distribution can be evaluated.

RbC 60 is known to exist in several stable phases as a function of temperature. Particularly interesting systems are obtained if the material is warmed up from a quenched low temperature cubic phase. Subsequently, a dimeric, a monomeric and a polymeric phase are obtained and were analysed by Raman spectroscopy. The dimeric phase is of particular interest, since it exhibits a textbook-like splitting of the degenerated H g modes and an unusual but very well expressed lack of any splitting for the G g modes. This allows a very straight correlation of the spectra to those of C 60 .

The reactivity of cysteines following cluster destruction by iron chelation was investigated for [4Fe-4S]2+ and cubane [3Fe-4S]+ beef heart aconitase. When the chelator orthobathophenanthroline disulfonate was used, the formation of sulfur-sulfur bonds and the retention of inorganic sulfur from the cluster was observed. For both the 4Fe and 3Fe forms of aconitase, the two cysteines in peptide 7, the cysteine in peptide 3, and the cysteine in peptide 2 were found as the primary constituents of sulfur-sulfur bonds (the peptide sequences and nomenclature are from Plank, D. W., and Howard, J. B. (1988) J. Biol. Chem. 263, 8184-8189). Three of these four cysteines (peptides 3 and 7) correlated with those proposed to be cluster ligands recently determined by x-ray crystallography (Robbins, A. H. and Stout, C. D. (1989) Proteins, in press; Robbins, A. H., and Stout, C. D.,, (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 3639-3643) for pig heart aconitase. A mechanism is proposed whereby the greater affinity of orthobathophenanthroline disulfonate for Fe2+ relative to Fe3+ shifts the equilibrium toward reduction of ferric iron through sulfur-sulfur bond formation at the cluster site. Aconitase which has been oxidized with ferricyanide and from which the cluster iron has been removed by EDTA has been shown to have two di- or polysulfides (Kennedy, M. C., and Beinert, H. (1988) J. Biol. Chem. 263, 8194-8198). The cysteines found in the sulfur-sulfur bonds generated by this treatment also were predominantly those from peptides 3 and 7. In addition, the putative thiol ligands for the linear [3Fe-4S]+ cluster of aconitase are reported. The four cysteines of peptides 7 and 9 (two in each peptide) were found to be protected by the cluster from alkylation when the protein was denatured. The difference in the ligands between the cubane and linear forms indicates that a specific thiol exchange occurs during the conversion.

In an accompanying paper (Kennedy, M. C., Spoto, G., Emptage, M. H., and Beinert, H. (1988) J. Biol. Chem. 263, 8190-8193), it was shown that one cysteine per mol of aconitase is modified by a variety of sulfhydryl reagents. We have identified the tryptic peptide that contains the iodoacetamide-reactive cysteine. We have also demonstrated that this cysteine is the primary site of modification by phenacyl bromide (2-bromoacetophenone), a spin label analogue of N-ethylmaleimide (HO-461) and iodoacetate in both the 3Fe and 4Fe forms of aconitase. The amino acid sequence of the peptide containing the reactive cysteine from beef heart aconitase shares no homology with the reactive cysteine-containing peptide reported for pig heart aconitase (Hahm, K.-S., Gawron, O., and Piszkiewicz, D. (1981) Biochim. Biophys. Acta 667, 457-461). We also report the amino acid compositions and sequences of seven other cysteine-containing tryptic peptides from beef heart aconitase. However, none of the cysteinyl peptides isolated were found to correspond to the reported pig heart reactive cysteinyl peptide. Evidence is also presented that no previously unreactive cysteine becomes exposed and reactive to sulfhydryl reagents in the conversion from the [4Fe-4S] cluster of the enzyme to the [3Fe-4S] cluster. We conclude from this that any potential cysteine ligand to the Fea site of the cluster must be inaccessible to solvent in the 3Fe form or, alternatively, that active 4Fe aconitase does not contain a cysteine ligand to the Fea site.