The fact that the peptide assembles in an expected fibril arrangement demonstrates the credibility of our conception of design. The discovery of a short peptide with fibril-forming ability and stimulus-sensitive behavior opens new opportunities for a number of applications.

We studied the conformation of a series of γ-ethyl-L-glutamate oligopeptides by circular dichroism and 220 MHz nuclear magnetic resonance spectroscopy. By use of the first technique we noted enhancement of the n → π * and splitting of the π → π * transitions commencing with the heptamer in trimethylphosphate and trifluoroethanol. With the second method we found changes in chemical shifts for the amide protons consistent with the onset of helicity at the heptamer in the solvents noted above. When DMSO- d 6 is used as a solvent, no such chemical shift changes occur because the oligopeptides do not assume helical conformations.

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Specific binding of an antibody to its antigen at subnanomolar concentrations has been detected electrically by impedance spectroscopy through changes in the ion‐conductance of a synthetic ligand‐gated ion channel (SLIC) in a supported lipid bilayer on a gold electrode (see picture).

The tuftsin retro-inverso analogue H-Thr psi[NHCO](R,S)Lys-Pro-Arg-OH was synthesized through a novel procedure for the high-yield incorporation of isolated retro-inverso bonds into peptide chains and the use of the new Meldrum's acid derivative (CH3)2C(OCO)2CH(CH2)4NHCOCF3 followed by its efficient coupling in solution to trimethylsilylated H-D-Thr(t-Bu)NH2. Closely related peptide impurities were eliminated both from the crude final peptide and the fully protected tetrapeptide amide precursor via ion-exchange and reversed-phase displacement chromatography, respectively. The tuftsin retro-inverso analogue proved to be completely resistant to enzymatic degradation in vitro, either against isolated aminopeptidases or human plasma proteolytic enzymes. When administered either orally or intravenously, it was significantly more active than normal tuftsin in increasing the number of specific antibody secreting cells in spleen of mice immunized with sheep erythrocytes. Furthermore, the analogue exerted an enhanced stimulatory effect on the cytotoxic activity of splenocytes against YAC-1 tumor cells. Finally, retro-inverso-tuftsin was about 10-fold more potent than the native peptide in reducing rat adjuvant arthritis. The resistance of the retro-inverso analogue to peptidases might explain the increased in vivo activities and allows its further immunopharmacological characterization.

We have previously shown that the priming of mice with live Mycobacterium tuberculosis var. bovis (Bacillus Calmette-Guérin, BCG) and immunization with the repetitive malaria synthetic peptide (NANP)40 conjugated to purified protein derivative (PPD), led to the induction of high and long-lasting titers of anti-peptide IgG antibodies, overcoming the requirement of adjuvants and the genetic restriction of the antibody response to the peptide (Lussow et al., Proc. Natl. Acad. Sci. USA 1990. 87:2960). This initial work led us to the following observations. BCG had to be live for priming to lead to the induction of anti-peptide antibodies. Surprisingly, priming with other living microorganisms which chronically infect the macrophage (e.g. Salmonella typhimurium and Leishmania major) also induced anti-peptide antibodies in mice immunized with PPD-(NANP)40 conjugate. It was, thus, hypothesized that molecules expressed during active infection and also known to be highly conserved between species, namely the heat-shock proteins (hsp), could mediate the T cell sensitization required for the production of anti-peptide antibodies. In fact, when the PPD protion of the conjugate was replaced by a highly purified recombinant protein corresponding to the 65-kDa (GroEL-type) hsp of M. bovis, this resulted in the production of anti-(NANP) IgG antibodies in BCG-primed mice, irrespective of the major histocompatibility complex-controlled responsiveness to the (NANP) sequence itself. Further, similar induction of anti-peptide antibody response was also obtained with a recombinant 70-kDa (DnaK-type) hsp of M. tuberculosis, but not with a small molecular mass (18 kDa) of M. leprae. Finally, an adjuvant-free carrier effect for anti-peptide IgG antibody production in BCG-primed mice, was also exerted by the GroEL hsp of Escherichia coli. This finding that hsp can act as carrier molecules without requiring conventional adjuvants is of potential importance in the development of vaccine strategies.

Tuftsin, a natural linear tetrapeptide (Thr-Lys-Pro-Arg) of potential antitumor activity, has been studied in DMSO-d6 solution by 2D NMR spectroscopy. 1H and 13C spectra show the presence of two families of conformations characterized by a trans or cis Lys-Pro bond, respectively. The family of conformers containing the cis peptide bond is a mixture of extended structures as expected for a short linear peptide. On the contrary, the trans isomer appears to be a rigid, folded conformer, as indicated by crucial NOEs and by the exceptionally low temperature coefficient of Arg NH. Analysis of the solution data by means of energy calculations leads to a unique structure, characterized by a Lys-Pro inverse gamma-turn.

SynopsisCircular dichroism (CU) measurements were carried out on various copolymers of L-tryptophan and r-ethyl L-glutamate in ethylene glycol monomethyl ether as the solvent. On increasing the L-tryptophan content of the copolymers a gradual change in the C D spectra was observed. The typical spectrum of the right-handed a-helix becomes more and more evident as the L-tryptophan content decreases. On the basis of these results we assumed that no conformational transition occurs on proceeding from pure poly (7-ethyl L-glutamate) to pure poly-Ltryptophan in ethylene glycol monomethyl ether: therefore the conformation of poly-L-tryptophan should be that of a right-handed a-helix. Moreover we observed that the change in the CD spectra of the copolymers is gradual but not linear on increasing the tryptophan content. The deviations from linearity were attributed to interactions among side-chain chromophores whose contributions to the optical activity are not simply additive. An x-ray analysis carried out on oriented films of poly-L-tryptophan casted from solutions of the polymer in dimethylformamide shows conclusively that the solid-state conformation of the polymer is that of an a-helix.