Spontaneous dynamics of magnetic islands depending on various plasma parameters in the Large Helical Device (LHD) are described. The structure of the magnetic island undergoes deformation during a discharge. There are two states of magnetic island; they are the growth and self-healing of the magnetic island. The self-healing occurs in the higher-beta and lower-collisionality plasmas. The magnetic island, on the other hand, grows in the lower-beta and higher-collisionality region. The self-healing phenomenon is realized by the disappearance of the local flattening of the T-e profile and the perturbed magnetic field structure compensating the externally imposed perturbation field to produce a seed magnetic island.

The total synthesis and structural characterization of the MHCII-associated p41 invariant chain fragment (P41icf) is described. P41icf plays a crucial role in the maturation of MHC class II molecules and antigen processing, acting as a highly selective cathepsin L inhibitor. P41icf synthesis was achieved using a combined solid-phase/solution approach. The entire molecule (65 residues, 7246 Da unprotected) was assembled in solution from fully protected peptides in the size range of 10 residues. After deprotection, oxidative folding in carefully adjusted experimental conditions led to the completely folded and functional P41icf with a disulfide pairing identical to that of native P41icf. CD, NMR, and surface plasmon resonance (SPR) were used for the structural and functional characterization of synthetic P41icf. CD thermal denaturation showed clear cooperative behavior. Tight cathepsin L binding was demonstrated by SPR. (1)H NMR spectroscopy at 800 MHz of unlabeled P41icf was used to solve the three-dimensional structure of the molecule. P41icf behaves as a well-folded protein domain with a topology very close to the crystallographic cathepsin L-bound form.

The conformation of α-conotoxin MI, a potent antagonist of the nicotinic acetylcholine receptor, has been investigated in aqueous solution. Two-dimensional NMR experiments and simulated annealing calculations provide the overall topology of α-conotoxin MI; then molecular dynamics simulation with the explicit solvent water was followed in order to obtain a more reliable solution structure. The resulting conformation indicates the presence of a 310 helix and a type I β-turn for residues Pro6–Cys8 and Gly9–Try12, respectively, and shows a significant structural similarity to that of α-conotoxin GI, which has biological activity similar to that of MI. The present study provides a molecular basis for the α-conotoxin–receptor interaction.

Peptide ScienceVolume 51, Issue 4 p. 245-246 Free Access Editorial: Chemical synthesis of proteins Shumpei Sakakibara, Shumpei SakakibaraSearch for more papers by this author Shumpei Sakakibara, Shumpei SakakibaraSearch for more papers by this author First published: 12 January 2004 https://doi.org/10.1002/(SICI)1097-0282(1999)51:4<245::AID-BIP1>3.0.CO;2-4Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume51, Issue41999Pages 245-246 RelatedInformation

During the assembly of the GFP molecule, we were able to confirm the usefulness of the solid-phase method for reducing the time to synthesize protected segments having a size of 10 to 12 residues. However, here I wish to clearly emphasize that all the segment-condensation reactions must be carried out in solution; that is, every step of the segment-condensation reactions must be carefully monitored by either TLC or HPLC and progression to the next step should only be done after confirming the homogeneity of the product. If it is not done, highly homogeneous products cannot be obtained even by the solution procedures. By applying this principle, it should be possible to synthe-size 100- or 200-residue peptides without any difficulty by the Boc/Bzl-strategy or probably even by the Fmoc/t Bu-strategy. The most important factor for realizing such a segment-condensation reaction in solution is the availability of powerful solvent systems such as mixtures of CHL/TFE, CHL/phenol, or CHL/HFIP, and a combination of useful coupling reagents, WSCD and HOOBt. I am optimistic about the total synthesis of GFP as we have not yet encountered any critical problem which would overturn our original expectations. By applying these methods, I am certain in general that we are able to synthesize an ordinary 100-residue protein within several months, and a 200-residue protein within a year. This approach should be the only possible way to synthesize such a large peptide in a homogeneous form by the chemical procedures.

An amino-terminal extension of endothelin-1 by the Lys-Arg dipeptide in the prosequence (KR-ET-1) greatly increased the ratio of native-type to non-native-type disulfide isomer (96/4 versus 71/29) during the oxidative folding reaction. This improvement was completely abolished by substituting Asn for Asp at position 8 (D8N-KR-ET-1), whereas most of it was maintained with similar carboxamide analogues replaced at Glu10 or Asp18. Structure analyses by circular dichroism spectroscopy revealed that (i) in the carboxylate state, the α-helical content of the native-type isomer of KR-ET-1 is higher than that of the native-type isomer of ET-1, while such a variation is not observed in the corresponding non-native-type isomer of KR-ET-1; and (ii) the enhanced α-helicity resulting from the Lys-Arg extension is largely diminished in D8N-KR-ET-1. From these results and our previous findings that the helical structure in KR-ET-1 is stabilized by a particular salt bridge between the extended Arg-1 basic moiety and either the Asp8 or Glu10 acidic side chain in ET-1 [Aumelas, A. et al., Biochemistry, 34 (1995) 4546], we conclude that the formation of a specific salt bridge between the side chains of Arg-1 and Asp8 in KR-ET-1 is critical for the predominant generation of the native-type disulfide isomer, probably because it stabilizes the helical structure of parental ET-1.

Midkine (MK), a retinoic acid-inducible growth/differentiation factor, serves as a substrate for tissue transglutaminase (Kojima, S., Muramatsu, H., Amanuma, H., and Muramatsu, T. 1995. J. Biol. Chem. 270, 9590-9596). Upon incubation with transglutaminase MK forms multimers through cross-linkages. Here, we report the following results. 1) Heparin potentiated the multimer formation by MK. 2) The N- and C-terminal half domains each formed a dimer through the action of transglutaminase. 3) Gln42 or Gln44 in the N-terminal half and Gln95 in the C-terminal half served as amine acceptors in the cross-linking reaction, as judged from the incorporation of putrescine into whole MK or each half domain, and the competitive inhibition of the cross-linking by MK-derived peptides containing Gln residue(s). The strongest inhibition was obtained with Ala41-Pro51. 4) This peptide abolished the biological activity of MK to enhance the plasminogen activator activity in bovine aortic endothelial cells. The inhibition was limited against the MK monomer, and not seen against the MK dimer, separated by gel filtration chromatography. These results suggest that dimer formation through transglutaminase-mediated cross-linking is an important step as to the biological activity of MK.

In a two-step selective disulfide-bond-forming reaction of human uroguanylin, a 16-residue peptide with two intramolecular disulfide bonds, two compounds (I and II) were formed, which could be detected by RP-HPLC after the second disulfide-bond-forming reaction and were isolated as single entities. Their primary structures, molecular weights, and disulfide connectivities proved to be identical, but their optical rotation values were different, suggesting that they are topological isomers. Only compound I was found to increase the cGMP levels in cultured T84 cells significantly. The ratio of these compounds was affected by the order of the disulfide-bond-forming reactions, but not by the solvent used. The presence of a carboxyl-terminal leucine residue seems to be crucial for stabilizing the conformation of the two isomers.