To confirm that Mycobacterium tuberculosis chaperonin 10 (Cpn10) is secreted outside the live bacillus, infected macrophages were examined by electron microscopy. This revealed that the mycobacterial protein accumulates both in the wall of the bacterium and in the matrix of the phagosomes in which ingested mycobacteria survive within infected macrophages. To understand the structural implications underlying this secretion, a structural study of M. tuberculosis Cpn10 was performed under conditions that are generally believed to mimic the membrane environment. It was found that in buffer-organic solvent mixtures, the mycobacterial protein forms two main species, namely, a partially helical monomer that prevails in dilute solutions at room temperature and a dimer that folds into a ␤-sheet-dominated structure and prevails in either concentrated protein solutions at room temperature or in dilute solutions at low temperature. A partially helical monomer was also found and was completely associated with negatively charged detergents in a micelle-bound state. Remarkably, zwitterionic lipids had no effect on the protein structure. By using N-and C-truncated forms of the protein, the C-and N-terminal sequences were identified as possessing an amphiphilic helical character and as selectively associating with acidic detergent micelles. When the study was extended to other chaperonins, it was found that human Cpn10 is also monomeric and partially helical in dilute organic solvent-buffer mixtures. In contrast, Escherichia coli Cpn10 is mostly dimeric and predominately ␤-sheet in both dilute and concentrated solutions. Interestingly, human Cpn10 also crosses biological membranes, whereas the E. coli homologue is strictly cytosolic. These results suggest that dissociation to partially helical monomers and interaction with acidic lipids may be two important steps in the mechanism of secretion of M. tuberculosis Cpn10 to the external environment.

The nature of the products arising from a 10 days, sterile incubation at 37°C and pH 7.2 of a 1:1 mixture of N-α-(p-tosyl)-lysine-methylesterhydrochloride and anhydrous D-glucose was investigated by fast atom bombardment mass spectrometry and(1)H and(13)C nuclear magnetic resonance spectroscopies. Differently to the reactivity usually described on the basis of other analytical techniques, FAB mass spectrometric measurements indicate the occurrence of the reaction of protected lysine with more than one D-glucose molecule.

The mass spectrometric behaviour of four differently substituted imidazoles and three 1,3 disubstituted imidazole iodides are discussed in detail with the aid of metastable-ion data, daughter-ion spectra, deuteriumlabelling experiments and comparison with model compounds. The results thus obtained indicate the presence of molecular species in an open, distonic ion structure and seem to exclude the occurrence of ring enlargement reactions that have been proposed in the literature.

The electron-impact induced fragmentation processes of nine differently N-substituted imidazoles were studied by means of mass-analyzed ion kinetic energy spectrometry. The compounds under study show a mass spectrometric behaviour different from that observed for other imidazoles already studied. In fact all the observed decompositions are related to the substituent chains.Imidazoles are compounds of high pharmacological interest, due to their inhibition properties against Tromboxane Mass spectrometry has been widely employed for their structural chara~terization.~ Noteworthy among the numerous papers on this topic are those due to Oashi et al. ', Gioia et a1.6 and Van Thujil,' which led to a clear description of the mass spectrometric behaviour of imidazole and imidazoline derivatives. More recently, the mass spectrometric behaviour of four differently substituted imidazole and three 1,3-disubstituted imidazole iodides were discussed by us and the results, obtained by metastable ion spectra, by labelling experiments and by comparison with model compounds, confirmed the presence of molecular species in the open, distonic ion structure already suggested by Gioia et a1.6 and seemed to exclude the occurrence of the ring enlargement reaction previously proposed in the literature.' Pursuing our interest in the mass spectrometric behaviour of imidazole derivative^,^ we report in the present paper a study performed on compounds 1-9 by means of electron ionization and metastable-ion experiments. EXPERIMENTAL Chemical synthesisCompound I . 1.23 g of sodium hydride was dissolved in 5mL of dimethylformamide. A solution of 2.57g of imidazole was slowly added dropwise to 5 mL of this solution. Then, heating at 90 "C, a solution of 8-bromo ottanoic acid in dimethylformamide was added. After standing at 90°C for 18h, the solution was concentrated, redissolved in water and extracted with chloroform; after a further concentration a white solid was obtained.Elemental analysis. Calculated: C 53.65%, H 7.72%, N 11.38%. Found: 53.70%, 7.76%, 11.40%. ylformamide was added, dropwise. After standing at 90°C for 22h, the solvent was evaporated under vacuum. The solid was redissolved in 400 mL of methyl chloride and then washed with water, obtaining the desired product as a white solid.Elemental analysis. Calculated: C 43.20%, H 7.25%, N 11.24%. Found: 44.62%, H 7.58%, N 11.06%.7.41; s(1H) 7.37; t(2H) 4.13; t(2H) 2.25; m(2H) 1.78; m(2H) 1.46; m(6H) 1.21. Compound 3 . 4.587 g of imidazolyl propanol was dissolved in 35 mL of tetrahydrofuran and then metallic sodium was added. 28mL of a solution of benzyl

The electron ionization mass spectrometric behaviour of ten 3-1 Z-(nitroxy)alkyl I -2H-1,3-benzoxazin-Q(3H)-one derivatives has been studied by means of metastable ion studies. By mass-analysed ion kinetic energy spectrometry of the related molecular ions, clear differences have been evidenced between the 5-methyl derivative and the other compounds, consisting of a highly favoured loss of NO, radical. The same methodology has allowed easy characterization of isomeric compounds.