Peptide Aß(16-25) Forms Nanofilms in the Process of Its Aggregation.

A method for the synthesis and high purification of fragments of Aß(1-42) peptide has been elaborated. We have synthesized the amyloidogenic fragment Aß(16-25) predicted by us and studied the process of its aggregation by electron microscopy and X-ray analysis. Electron microscopy images show that the peptide forms a film, which is not characteristic of amyloid fibrils. At the same time, according to the X-ray diffraction data, its preparations display the presence of two main reflections (4.6-4.8 and 8-12 Å) characteristic of cross-ß structure of amyloid fibrils. Thus, the fragment Aß(16-25) that we predicted is a promising object not only for studying the process of polymerization of the peptides/proteins, but also for using it as a nanomaterial to study a number of biological processes.

[Synthesis and antibacterial activity of analogues of the N-terminal fragment of the sarcotoxin IA antimicrobial peptide]. / Sintez i antibakterial'naia aktivnost' analogov N-kontsevogo fragmenta antimikrobnogo peptida sarkotoksina IA.

Three 18-membered analogues of the N-terminal fragment of the sarcotoxin IA cationic antimicrobial peptide were synthesized by the solid phase method of peptide synthesis with the use of swellographic monitoring. The ability of these peptides to inhibit the growth of various bacteria in culture medium and their hemolytic activity in experiments on human erythrocytes were studied. The analogue completely corresponding to the N-terminal amino acid sequence of the natural sarcotoxin IA with the amide group on its C-terminus exhibited higher antibacterial activity. The presence of carboxyl group on the C-terminus or the substitution of Tyr for Trp2 resulted in a decrease in the antimicrobial activity of the peptide. Our results indicate that the amphiphilic N-terminal peptide corresponding to the 1-18 sequence of sarcotoxin IA involves the moieties responsible for the antimicrobial activity of the antibiotic.

Self-aggregation properties of spin-labeled zervamicin IIA as studied by PELDOR spectroscopy.

In this article, the pulsed double electron-electron resonance in electron spin-echo (PELDOR) technique is applied to study the self-aggregation of spin-labeled zervamicin IIA, a hexadecapeptide antibiotic of fungal origin, which is known to form ion channels in a phospholipid double layer. Measurements of the ion channel forming properties and the antibiotic activity of the analog indicate that replacement of the C-terminal phenylalaninol by the amino-2,2,6,6-tetramethylpiperidinyloxy (TEMPO) residue does not influence the biophysical and biological properties. The dipole-dipole interaction between the spin labels of the fully biologically active peptide analog was studied in frozen (77 K) glassy solutions in different ratios of toluene-methanol. The spin-labeled zervamicin IIA molecules were shown to form aggregates. An average distance between the spin labels in the aggregates was estimated to be in the range of 25-35 A (depending on the solvent composition), indicating that the amphiphilic helical peptide molecules are oriented in an antiparallel fashion. Increasing of methanol content in the solution results in a loosening of the aggregate structure. It was shown that the fraction of aggregated zervamicin IIA molecules is less than 44-67% depending on the solvent composition. The general usefulness of the method to obtain structural long-range information in a range of several tens of angstroms is demonstrated by comparison with the peptide cluster of trichogin GA IV.

Pressure monitoring of continuous-flow solid-phase peptide synthesis.

We describe the noninvasive real-time pressure monitoring of Boc- and Fmoc-based peptide synthesis. Pressure was measured using a resistance strain gauge attached to the inlet of a continuous-flow reactor of variable volume. In the assembly of the 'difficult' polyalanine sequence, it was shown that pressure monitoring can reveal structural variations of the peptide-resin, e.g. the onset, development and termination of aggregation. This method provided washing minimization that favored substantial saving of solvents. The obtained results demonstrated the advantage of pressure monitoring over swellographic monitoring.

Spectrophotometric monitoring in continuous-flow Boc-based solid-phase peptide synthesis.

It has been demonstrated that SPPS with Boc amino group protection can be monitored spectrophotometrically if it is performed in a continuous-flow reactor of variable volume. It is shown that this approach provides useful and adequate evidence on the beginning/end-point of most steps of the SPPS cycle. At the deprotection step the spectrophotometric monitoring enables real-time recording of the initial and final moments of the process. When synthesizing a 'difficult' polyalanine sequence, we were able to monitor variation in the deprotection dynamics associated with the aggregation phenomena. The time actually necessary for the Boc protecting group removal appeared to be significantly smaller than that usually preset in the available Boc-SPPS protocols.

[The automated "SynChrom" system for solid-phase synthesis of peptides and liquid column chromatography. I. Principles of design and structural constituents]. / Avtomatizirovannyi kompleks dlia tverdofaznogo sinteza peptidov i zhidkostnoi kolonochnoi khromatografii "SinKhron". I. Printsipy postroeniia i strukturnye sostavliaiushchie.

An automatic modular SynChrom system was designed for solid phase synthesis and chromatographic purification of peptides. Structural constituents and organization and operation of the system in solid phase peptide synthesis and liquid column chromatography modes are described. Swellographic monitoring of the course of synthesis was used. Hydraulic diagrams, operation algorithm and software description are presented.

[The automated "SynChrom" system for solid-phase synthesis of peptides and liquid column chromatography. II. Use in the solid-phase synthesis of peptides and liquid column chromatography]. / Avtomatizirovannyi kompleks dlia tverdofaznogo sinteza peptidov i zhidkostnoi kolonochnoi khromatografii "SinKhrom". II. Ispol'zovanie v tverdofaznom sinteze peptidov i zhidkostnoi kolonochnoi khromatografii.

Automatic solid phase peptide synthesis using the SynChrom system is described. Problems of swellographic monitoring are discussed. Combined monitoring (swellographic, spectrophotometric, and manometric) of all steps of the synthetic cycle are suggested. Potential applications of the system to liquid column chromatography were demonstrated.

[Optimization of a protocol for automatic solid phase synthesis of peptides using a variable volume flow reactor]. / Optimizatsiia protokola tverdofaznogo avtomaticheskogo sinteza peptidovs ispol'zovaniem protochnogo reaktora peremennogo ob''ema]

The protocol for solid phase peptide synthesis using automatic synthesizers MilliGen/Biosearch 9500 and 9600 with built-in variable volume flow-reactors has been elaborated. The data of swellographic monitoring were used for optimization of process parameters. The peptides involving from 10 to 21 amino acid residues were synthesized using developed protocol. Significant economy of reagents and solvents has been demonstrated for synthesis of good quality peptides.