Experimental NMR diffusion measure on polymers and on globular proteins are presented. These results, complemented with results found in the literature, enable a general description of effective fractal dimension for objects such as small organic molecules, sugars, polymers, DNA, and proteins. Results are compared to computational simulations as well as to theoretical values. A global picture of the diffusion phenomenon emerges from this description. A power law relating molecular mass with diffusion coefficients is described and found to be valid over 4 orders of magnitude. From this law, the fractal dimension of the molecular family can be measured, with experimental values ranging from 1.41 to 2.56 in full agreement with theoretical approaches. Finally, a method for evaluating the molecular mass of unknown solutes is described and implemented as a Web page.

Substance P, one of the mammalian tachykinins, is known to interact strongly with lipid bilayers and this interaction may play a role in the receptor–peptide recognition process. The conformation of substance P bound to vesicles consisting of perdeuterated phosphatidylcholine has been investigated by means of two‐dimensional transferred nuclear Overhauser (trNOE) spectroscopy. Nuclear magnetic resonance data analysis resulted in a unique conformational family characterized by a well‐defined conformation of the last seven C‐terminal amino acids, which consists of a sequence of nonstandard turns following each other in a helix‐like manner. The absence of short‐ or medium‐range trNOE in the N‐terminal part indicates its structural flexibility. © 2000 John Wiley & Sons, Inc. Biopoly 54: 297–306, 2000

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SUMMARYThree strains of methylotrophic yeasts, Candida boidinii, Pichia angusta (previously Hansenula polymorpha) and Pichia pastoris, were studied for their capacity to grow on methanol in deuterated media.Growth rates, determined relative to the extent of deuteration of water and/or methanol, showed that water deuteration was the major limiting factor. After adaptation to deuterium by progressive transfer through media of increasing deuteration, growth rates were diminished relative to those obtained on hydrogenated media of identical salts composition: the two Pichia species retained the highest growth rates (p = 0.02 h-1) in the fully deuterated medium. Perdeuterated biomass (16 g) was obtained in a 1 liter fed-batch fermentation and the extent of deuteration of isolated ergosterol has been shown to be 97.5% by mass spectrometric analysis .

GPL X-1, a novel glycopeptidolipid (GPL) isolated from Mycobacterium xenopi ( C q 140 35004), has recently been found to typify a new class of mycobacterial glycopeptidolipids devoid of C-mycoside core structure, the so-called serine-containing glycopeptidolipid [Rivikre, M. & Puzo, G. (1991) J. Biol. Chem. 266,9057-90631. Here we report the purification and characterization of a novel serine-containing GPL termed GPL X-IIb, isolated from the M. xenopi strain NCTC 10042.On thin-layer chromatography, this GPL was found to be present in some other M. xenopi strains isolated from patients with pulmonary infections. The sugar and amino-acid compositions of this GPL were elucidated from the native form using a combination of two-dimensional homonuclear and heteronuclear scalar coupling NMR. The peptide and sugar sequences, as well as the methoxyl group locations on the C-3 of the 6-deoxy-a-~-talopyranoside (6dTalp) and on a Ser, were unambiguously determined by heteronuclear multiple-bond correlation experiments. GPL X-1% was found to be composed of a lipotetrapeptide of the following structure C,,-Ser-OMe-Ser-Phe-a%-OMe (aThr = allothreonine). The sugar part is made up of 30Me-a-~-6dTalp and the following disaccharide : a-~-Rhap-(1+3)-2-O-Lau-a-~-Rhap (Rhap = rhanmopyranose). Unlike GPL X-I, the sugar attachment sites on the tetrapeptide were successfully determined from heteronuclear three-bond coupling correlation observed in the heteronuclear multiple bond correlation spectrum between the anomeric carbon resonances and the protons of aThr-OMe and Ser. It was established that the 30Me-6dTalp glycosylates the Ser while the disaccharide is linked to the aThr-OMe. Thus both GPL X-I and GPL X-IIb share a common lipotetrapeptide core [with the exception of Ser(0Me)l but drastically differ in their oligosaccharide appendage. Thus, by analogy with the M. avium complex, the present report suggests that M. xenopi species can be divided in various serovars characterized by the unique structure of their C-mycoside GPL oligosaccharide appendage, enhancing the interest for this new type of serine-containing glycopeptidolipid.Research into mycobacterial infection has intensifying as a result of a resurgence in the prevalence of human tuberculosis. In developed countries, the epidemiology of the disease is changing, due mainly to the emergence of drug-resistant Mycobacterium tuberculosis strains (Weiss, 1992), but also from an increase in infections with nontuberculous mycobacteria such as Mycobacterium avium, Mycobacterium kansasii Correspondence to M.

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