Spectroscopy - Volume 17, issue 4

Authors: Esquieu, Didier | Péloponèse, Jean‐Marie | Opi, Sandrine | Gregoire, Catherine | de Mareuil, Jean | Watkins, Jennifer | Campbell, Grant | Dunot, Jean‐Pierre | Sturgis, James | Witvrouw, Myriam | Pannecouque, Christophe | de Clercq, Erik | Montembault, Mickaël | Giang, Vo‐Thanh | Villiéras, Monique | Fargeas, Valérie | Lebreton, Jacques | Loret, Erwann P.

Article Type: Research Article

Abstract: Tat is a regulatory HIV‐1 protein, which has the particularity to be secreted very early by HIV‐infected cells. The extra cellular roles of Tat are suspected to be the main cause of the maintenance of reservoirs of HIV‐infected cells and the failure of actual AIDS therapies to eradicate HIV. This study describes the rationale used to design molecules that bind to a target area containing an hydrophobic pocket identified in the 2D‐NMR structure of Tat. Molecules were synthesized and the derivative named TDS2 was shown to be a Tat inhibitor. Fluorescence revealed that TDS2 binds in the target area, which …is conserved across five different Tat variants representative of the main HIV‐1 subtypes. TDS2 inhibited in vitro HIV‐1 replication in human T‐cells. Further chemical modifications remain necessary to enhance affinity to Tat and reduce cytotoxicity. Show more

Citation: Spectroscopy, vol. 17, no. 4, pp. 639-645, 2003

Authors: Ventura, Salvador | Serrano, Luis

Article Type: Research Article

Abstract: The aggregation of proteins in fibrillar form is a problem of critical importance in a wide range of abnormal disease states. To decipher the molecular mechanism of formation of protein fibrillar aggregates we have chosen to study as model SH3 domains that exhibit different abilities to polymerize into amyloid fibrils. While being not related to any known disease, the SH3 domain of the p85α subunit of phosphatidylinositol 3 kinase has been found to form amyloid fibrils in vitro under acidic conditions, meanwhile, we have found that the spectrin SH3‐domain, sharing the same fold and some sequential identity keeps its native …conformation under the same conditions. The use of spectroscopic methods to study these properties is illustrated in the present job, and correlated to direct sample observation by electron microscopy. Show more

Keywords: Amyloid formation, UV, fluorescence, circular dichroism, SH3 domain

Citation: Spectroscopy, vol. 17, no. 4, pp. 647-652, 2003

Authors: Miles, Andrew J. | Wien, Frank | Lees, Jonathan G. | Rodger, A. | Janes, Robert W. | Wallace, B.A.

Article Type: Research Article

Abstract: Synchrotron radiation circular dichroism (SRCD) is an emerging technique in structural biology with particular value in protein secondary structure analyses since it permits the collection of data down to much lower wavelengths than conventional circular dichroism (cCD) instruments. Reference database spectra collected on different SRCD instruments in the future as well as current reference datasets derived from cCD spectra must be compatible. Therefore there is a need for standardization of calibration methods to ensure quality control. In this study, magnitude and optical rotation measurements on four cCD and three SRCD instruments were compared at 192.5, 219, 290 and 490 nm. …At high wavelengths, all gave comparable results, however, at the lower wavelengths, some variations were observable. The consequences of these differences on the spectrum, and the calculated secondary structure, of a representative protein (myoglobin) are demonstrated. A method is proposed for standardising spectra obtained on any CD instrument, conventional or synchrotron‐based, with respect to existing and future databases. Show more

Citation: Spectroscopy, vol. 17, no. 4, pp. 653-661, 2003

Authors: Want, Elizabeth | Greig, Michael | Compton, Bruce | Bolaños, Ben | Siuzdak, Gary

Article Type: Research Article

Citation: Spectroscopy, vol. 17, no. 4, pp. 663-680, 2003

Authors: Want, Elizabeth | Compton, Bruce Jon | Hollenbeck, Thomas | Siuzdak, Gary

Article Type: Research Article

Citation: Spectroscopy, vol. 17, no. 4, pp. 681-691, 2003

Authors: Prenni, Jessica E. | Shen, Zhouxin | Trauger, Sunia | Chen, Wei | Siuzdak, Gary

Article Type: Research Article

Abstract: This paper presents a novel combination of off‐line liquid chromatography (LC) separation with desorption ionization on silicon mass spectrometry (DIOS‐MS) as an alternative to the traditional on‐line coupling of LC and electrospray ionization (ESI). In this work, electrospray deposition is used to generate a spatially preserved linear track of the separated sample on a specially designed DIOS chip. The total sequence coverage analysis of two model protein systems was evaluated by both LC‐DIOS‐MS and nanoLC ESI tandem MS (MS/MS). LC‐DIOS‐MS yielded improved sequence coverage for both of the model systems (between 99.5 and 100%) compared with traditional LC‐ESI‐MS/MS analysis (between …82 and 87.6%). In addition to improved sequence coverage determination, LC‐DIOS‐MS also offers the potential for high‐throughput protein characterization. Show more

Citation: Spectroscopy, vol. 17, no. 4, pp. 693-698, 2003

Authors: Compton, Bruce Jon | Siuzdak, Gary

Article Type: Research Article

Abstract: Mass spectrometry is now widely used in many areas of biomolecule analysis and this diversity is well represented by the analysis of oligonucleotides, carbohydrates and steroids. In this paper an overview of the common techniques used for analysis of these biomolecules is presented, including electrospray ionization (ESI), matrix‐assisted laser desorption/ionization (MALDI), desorption/ionization on silicon (DIOS), and negative chemical ionization gas chromatography mass spectrometry (NCI GC/MS). Additionally, important aspects of biomolecule analysis, such as molecular weight determination, sequencing using tandem mass spectrometry and enzymes, precursor ion scanning, noncovalent interactions, and sensitivity, will be discussed.

Citation: Spectroscopy, vol. 17, no. 4, pp. 699-713, 2003

Authors: Zhou, Lei | Juneau, Gary | Xiong, Xiang | Lai, Helen W.L. | Yew, David T. | Lam, Kwok‐Wai

Article Type: Research Article

Abstract: Our recent report has described the occurrence of a remarkably high amount of an unknown compound with light absorption maximum at 290 nm in the aqueous humor of Black Moor goldfish. The absorption maximum is shifted to 270 nm in 0.01% trifluroacetic acid. The concentration of this compound was very low in the eye of common goldfish and was absent in ocular fluids or serum of mammalian species. This compound was isolated by chromatography on a carbohydrate column eluted by 10 mM ammonium phosphate followed by chromatography on a Delta PAK C18 column eluted by acetonitrile–water–trifluoroacetic acid. The ion …size of the unknown compound determined by electrospray for protonated and deprotonated ions are m/z 205 and 203, respectively. The protonated ion was fragmented to m/z 187, 169, 157 and 141 as the cone voltage increased. The data from mass spectrometry and nuclear magnetic resonance spectroscopy indicate the chemical structure of a carbohydrate with 7 carbons containing a lactone ring. Show more

Keywords: Goldfish, aqueous humor, megalophthalmia, high pressure liquid chromatography, mass spectrometry, nuclear magnetic resonance

Citation: Spectroscopy, vol. 17, no. 4, pp. 715-724, 2003

Authors: Burlot, Ludovic | Cherton, Jean‐Claude | Convert, Odile | Correia, Isabelle | Dennetiere, Bruno

Article Type: Research Article

Abstract: This paper deals with the cytotoxic chaetoglobosins obtained from culture on maize of the strains ATCC 26115 and MRC 2654 of the fungus Phomopsis leptostromiformis. Both strains produced, in more or less important amounts, the known chaetoglobosins M (1) and N (2). In addition, the new chaetoglobosin O (3), was isolated from the ATCC 26115 strain and characterized by HRMS and 2D NMR experiments. With the MRC 2654 strain, a fungal metabolite 4, more polar than the chaetoglobosins M and N, was extracted and purified. Spectroscopic and chromatographic data of metabolite 4 led to its identification to the bridged chaetoglobosin …named compound S, which previously has been obtained by intramolecular Michael reaction on the chaetoglobosin M. Moreover, a methylation under Williamson conditions of the chaetoglobosin 4 resulted in the formation of the trimethylated chaetoglobosin 5. Show more

Citation: Spectroscopy, vol. 17, no. 4, pp. 725-734, 2003

Authors: Jankowski, Christopher K. | Laouz, Antoun Bou | Lesage, Denis | Diaz T., Eduardo

Article Type: Research Article

Abstract: Dihalocyclopropanation of the double bond of some olefins, leading to dihalocyclopropanes, offered an opportunity to perform their rearrangement to dihalomethylvinyl with Hiyama type reagents, in presence of cationic system such as Cr2+ /Cr3+ . The chain elongation of alkenes via the gem‐dihalocyclopropanes produced α,β‐unsaturated aldehydes and acids.

Citation: Spectroscopy, vol. 17, no. 4, pp. 735-745, 2003

Authors: Salman, Salman R. | Kamounah, Fadhil S.

Article Type: Research Article

Abstract: Tautomeric equilibria in intramolecularly hydrogen bonded Schiff bases is studied on the basis of solution 13 C NMR chemical shifts. NMR spectroscopic data and comparison with two anils model compound, namely, salicylideneaniline (1A) and naphthalylidinequinoline (2A) were used to represent the enol (A) and the keto (H) forms. The 13 C NMR chemical shifts data of the novel series 4A (compounds, 4‐12) were used together with the values 13 C chemical shifts data of compounds 1A and 2A to calculate the % keto form. The calculated % keto form of 3A was compared to that calculated for series 4A compounds.

Keywords: Carbon‐13 chemical shift, keto–enol equilibrium, UV‐Vis spectroscopy, 1‐hydroxy‐2‐naphthaldehyde Schiff bases, percentage of the keto form

Citation: Spectroscopy, vol. 17, no. 4, pp. 747-752, 2003

Authors: Rhodes, Christopher J. | Tran, Thuy T. | Denton, Philip | Morris, Harry

Article Type: Research Article

Abstract: Using Transition‐State Theory, experimental rate constants, determined over a range of temperatures, for reactions of vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs Free Energies, for the overall reactions. Within the Linear Free Energy Relationship (LFER) assumption, that the Gibbs Free Energy of activation is proportional to the overall Gibbs Free Energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of …interest, involving potential antioxidants. Show more

Citation: Spectroscopy, vol. 17, no. 4, pp. 753-762, 2003

Article Type: Other

Citation: Spectroscopy, vol. 17, no. 4, pp. 763-770, 2003