NMR structural elucidation of myelin basic protein epitope 83-99 implicated in multiple sclerosis

Myelin basic protein peptide 83-99 (MBP83-99) is the most immunodominant epitope playing a significant role in the multiple sclerosis (MS), an autoimmune disease of the central nervous system. Many peptide analogues, linear or cyclic have been designed and synthesized based on this segment in order to inhibit the experimental autoimmune encephalomyelitis, the best well-known animal model of MS. In this study, the solution structural motif of MBP(83-99) has been performed using 2D (1)H-NMR spectroscopy in dimethyl sulfoxide. A rather extended conformation, along with the formation of a well defined alpha-helix spanning residues Val(87)-Phe(90) is proposed, as no long-range NOE are presented. Moreover, the residues of MBP peptide that are important for T-cell receptor recognition are solvent exposed. The spatial arrangement of the side chain all over the sequence of our NMR based model exhibits great similarity with the solid state model, while both TCR contacts occupy the same region in space.

In position 7 L: - and D: -Tic-substituted oxytocin and deamino oxytocin: NMR study and conformation

Incorporation of L: - or D: -Tic into position 7 of oxytocin (OT) and its deamino analogue ([Mpa(1)]OT) resulted in four analogues, [L: -Tic(7)]OT (1), [D: -Tic(7)]OT (2), [Mpa(1),L: -Tic(7)]OT (3) and [Mpa(1),D: -Tic(7)]OT (4). Their biological properties were described by Fragiadaki et al. (Eur J Med Chem 42:799-806, 2007). Their NMR study (NOESY, TOCSY, (1)H-(13)C HSQC spectra) is presented here. Analogues 1, 3 and 4 showed partial agonistic activity, analogue 2 was pure antagonist, suggesting that a cis conformation between residues 6 and 7 of the molecule does not result in antagonistic activity. However, the reduction in agonistic activity of analogues 1, 3 and 4 in comparison to oxytocin is consistent with the reduction of the trans conformation form. Binding affinity for the human oxytocin receptor with IC(50) value of 130, 730, 103, and 380 nM for peptides 1, 2, 3, and 4, respectively, showed lower affinity in the case of D: analogues. Deamination slightly increased the affinity. The existence of both cis and trans configurations of the Cys(6)-D: -Tic(7) bond is supported by observation of two sets of cross-peaks for (1)H and (13)C nuclei for most of the residues of the peptide not only in NOESY and TOCSY but also in (1)H-(13)C HSQC spectra. The MS and HPLC indicate the presence of a single molecule/peptide, and NMR data thus suggest that this second set of peaks is due to the cis conformation.

Amino Acids. 2010 Jan 27. PMID: 20108008

Study of a lipophilic captopril analogue binding to angiotensin I converting enzyme.

Human ACE is a central component of the renin-angiotensin system and a major therapeutic target for cardiovascular diseases. The somatic form of the enzyme (sACE) comprises two homologous metallopeptidase domains (N and C), each bearing a zinc active site with similar but distinct substrate and inhibitor specificities. In this study, we present the biological activity of silacaptopril, a silylated analogue of captopril, and its binding affinity towards ACE. Based on the recently determined crystal structures of both the ACE domains, a series of docking calculations were carried out in order to study the structural characteristics and the binding properties of silacaptopril and its analogues with ACE.

J Pept Sci. 2010 Feb;16(2):91-7.

PMID: 20014331

The HN(COCA)HAHB NMR experiment for the stereospecific assignment of Hbeta-protons in non-native...

The HN(COCA)HAHB NMR experiment for the stereospecific assignment of Hbeta-protons in non-native states of proteins

(3)J(H(alpha),H(beta))-coupling constants deliver precious information on the population of the three favored chi(1)-rotamers in unfolded states of proteins. Here, a novel pulse sequence, tailored toward the NMR analysis of non-native states of proteins, the HN(COCA)HAHB experiment, is developed to measure (3)J(H(alpha),H(beta)). In four subsequent INEPT steps, magnetization is transferred from H(N) to H(alpha). In a COSY-like magnetization transfer step, dephasing of magnetization on H(alpha) is quantified to determine the (3)J(H(alpha),H(beta))-coupling constants. Analysis of the measured homonuclear coupling constants, together with measurement of heteronuclear (3)J(N,C(gamma))- and (3)J(C',C(gamma))-coupling constants, allows stereospecific assignment of the two diastereotopic H(beta)-protons even in unfolded states of proteins, and the derivation of populations according to a Pachler-type analysis.

Journal of the American Chemical Society 2010;132(3):918-9.

Weiterbildung in Europa: Wie punkten wir?

Mit dem kürzlich in Kraft getretenen Vertrag von Lissabon wurde die Europäische Union demokratischer und verfügt über mehr Instrumente, um einheitlich nach aussen zu treten. "Aussen", das sind unter anderen wir - die Schweiz. Als 7.7-Mio.-Inselstaat unmitten Europas gegenüber 500 Mio. EU-Bürgern steht der Zugang zur internationalen Weiterbildung vor Herausforderungen. Wie positionieren wir uns? Durch Internationalisierung, Öffnung und freien Wissensfluss? Dieser Artikel vermittelt einen Überblick über die EU-Bildungsprogramme und die gängigen Punktesysteme für die Qualitätsmessung.