Agnieszka Godziek

On Spontaneously Pulsating Proline-Phenylalanine Peptide Microfibers.

Earlier, we have collected an experimental evidence showing that low molecular weight chiral carboxylic acids (amino acids included) can spontaneously undergo an oscillatory chiral conversion and an oscillatory condensation in abiotic aqueous and non-aqueous liquid systems, stored for certain amount of time under mild external conditions. These earlier findings are summarized in the introductory part of this study. In the second part, a preliminary report is given on spontaneous pulsation of peptide microfibers in the aged proline-phenylalanine (Pro-Phe) solution in 70% aqueous acetonitrile. The experimental evidence originates from a number of advanced analytical techniques. In view of our earlier and present findings, a presumption is made that the mechanism of spontaneous pulsation (formation and decay) of Pro-Phe microfibers is directly related to the oscillatory chiral conversion and oscillatory peptidization. The entity of the discussed results pointing out to spontaneous and uncontrolled instability of peptide structures might be a bad prognostic for employing such structures in nanobiotechnology.

Condensation Dynamics of the L-Pro-L-Phe and L-Hyp-L-Phe Binary Mixtures in Solution

We employ the achiral liquid chromatography with diode array, evaporative light scattering and mass spectrometric detection (HPLC-DAD, HPLC-ELSD and LC-MS) to assess structural instability (understood as spontaneous oscillatory chiral conversion and spontaneous oscillatory condensation) of the two pairs of amino acids, L-proline-L-phenylalanine (L-Pro-L-Phe) and L-hydroxyproline-L-phenylalanine (L-Hyp-L-Phe), in aqueous acetonitrile. In our earlier studies, we managed to demonstrate that single amino acids in aqueous and non-aqueous solutions undergo spontaneous oscillatory chiral conversion and oscillatory condensation. We also investigated condensation in the binary L-Pro-L-Hyp mixture in aqueous solution, and proposed a theoretical model to explain the specific dynamics of this process, which involves mutual catalytic effects of the two amino acids. In this study, we demonstrate oscillatory instability with the other two amino acid pairs in the organic-aqueous solution and reflect on the dynamics of condensation in the investigated cases. The choice of L-Pro and L-Hyp is due to their important role as building blocks of collagen, which is omnipresent in the connective tissues of mammals, and largely responsible for tissue architecture and strength. L-Phe is one of the 20 exogenous amino acids and is a building block of the majority of naturally occurring proteins.

Thin-layer chromatographic investigation of l-cysteine in solution

Spontaneous oscillatory chiral conversion and condensation of low-molecular-weight chiral carboxylic acids have been investigated by our research group for almost 10 years now. However, dynamics of these oscillatory processes substantially differ from one compound to another, moreover, spontaneous chiral conversion and condensation of sulfur-containing amino acids have not been investigated so far. To this effect, we present in this paper the results of our current investigations on spontaneous oscillatory chiral conversion and condensation of L-cysteine (L-Cys), a biologically important sulfur-containing semiessential amino acid. In our thin-layer chromatographic experiments, we employ the Mn(II) and Zn(II) cations to facilitate the enantioseparation of L-Cys from the spontaneously formed D-Cys, to prevent chiral conversion of the L form, and to highlight rapid consumption of Cys in the course of condensation. Spontaneous peptidization of Cys is confrmed with use of thin-layer chromatography-mass spectrometry (TLC-MS). Additionally, we emphasize the oscillatory nature of the investigated process with use of high-performance liquid chromatography-evaporative light scattering detection (HPLC-ELSD) and provide a complementary insight in the chemical structure of the spontaneously formed Cys-derived oligopeptides with use of HPLC-MS.

HPLC Monitoring of Spontaneous Non-Linear Peptidization Dynamics of Selected Amino Acids in Solution

This is our new study in a series of publications devoted to exploration of applicability of high-performance liquid chromatography (HPLC) to providing answers to difficult questions from the area of the reaction kinetics and mechanisms with non-linear reactions. Although an excellent analytical performance of HPLC is an indisputable fact, so far its performance as a tool in the kinetic and mechanistic studies has been tested to a lesser extent. In our earlier studies, spontaneous peptidization dynamics of amino acids in solution was demonstrated by means of HPLC upon a few amino acid examples, and on that basis a theoretical model has been developed, anticipating an interdependence of dynamics on chemical structures of amino acids involved. In order to expand the spectrum of experimentally investigated amino acid cases, in this study we present the results valid for three novel amino acids of significant life sciences importance, which differ in terms of peptidization dynamics. Experimental evidence originates from the achiral HPLC with the evaporative light scattering detection and MS detection. A conclusion is drawn that different spontaneous peptidization dynamics of amino acids may significantly influence chemical composition of proteins encountered in living organisms. Hence, a need emerges for systematic physicochemical studies on spontaneous non-linear peptidization dynamics of proteinogenic amino acids in liquid abiotic (but also in the biotic) systems.

Spontaneous Pulsation of Peptide Microstructures in an Abiotic Liquid System

We report observations of pulsating peptide formation and depeptidization in 70% aqueous acetonitrile solutions of l-Pro-l-Phe and l-Cys, resulting in the oscillatory appearance and disappearance of solid masses of microfibers and microspheres, respectively. We monitor the concentration changes of the monomeric amino acids by high-performance liquid chromatography. The concentration of all amino acid solutions used is 1.0 mg mL(-1), due to solubility limitations in 70% aqueous acetonitrile. The nonlinear concentration changes of l-Pro, l-Phe and l-Cys, and the amounts of the main peptidization products observed within our monitoring periods (for l-Pro-l-Phe, 250 h, and for l-Cys, 70 h) are typically from several to 20% of the original monomer concentrations. We follow the formation and decay of the insoluble peptides by turbidimetry. We also investigate the materials formed using scanning electron microscopy and mass spectrometry. We carry out numerical simulations on a simple model that reflects the main features of spontaneous pulsation of peptide fiber or sphere formation in this abiotic liquid system.

Investigation of Spontaneous Chiral Conversion and Oscillatory Peptidization of L-Methionine by Means of TLC and HPLC

From our earlier studies, it comes out that proteinogenic amino acids undergo spontaneous oscillatory chiral conversion and condensation. An understanding of these phenomena is crucial in view of the fact that amino acids are the building blocks of proteins and peptides present in all living organisms. Moreover, amino acids play an increasingly important role as components of drugs, dietary supplements, and cosmetics. In this study, we trace spontaneous oscillatory reactions of L-methionine (L-Met) with use of thin-layer chromatography with densitometric and mass spectrometric detection, and high-performance liquid chromatography with evaporative light scattering detection. Additional measurements were carried out with use of scanning electron microscopy. The results obtained confirm that L-Met spontaneously undergoes chiral conversion and peptidization. As an outcome of these two processes, peptides are formed of considerably different chemical structures, able to self-organize in nano- and microstructures under the mild ambient conditions without any catalysts.

Turbidity patterns of spontaneous peptidization in an aqueous abiotic system and possible secondary peptide structures

The non-linear dynamics of spontaneous peptidization running in 10 monocomponent and binary abiotic liquid systems of L- and D-Ala and L- and D-Phe is investigated with use of turbidimetry with continuous registration, high-performance liquid chromatography with light scattering detection (HPLC-ELSD), mass spectrometry (MS), and spectroscopy of far UV circular dichroism (CD). The turbidity patterns represent a sum of the light scattering effects caused by insoluble peptides of unknown yields, structures, and molecular weights. The auxiliary analytical techniques confirm the non-linear nature of peptidization (HPLC-ELSD) and spontaneous formation of the homo- and heteropeptides (MS). CD spectroscopy seems to confirm the presence of the secondary α-helix structures. The similarity of turbidity patterns is revealed with the monocomponent (L or D) and binary (L-L or D-D) systems of equichiral α-amino acids, and dissimilarity of patterns is observed with the binary systems of inequichiral α-amino acids (L-D). The tentative conclusion is drawn that the peptides assembled of equichiral α-amino acid units are able to assume the secondary (right- or left-handed α-helix) structures, which in a certain way could foster the similarity of turbidity patterns, and the peptides built of inequichiral α-amino acid units cannot ensure an efficient enough stringing of monomer molecules into equichiral heptades to form complete segments of an α-helix. This randomness of the α-amino acids arrangement in the inequichiral peptide molecules most probably manifests itself as a lack of similarity among the respective turbidity patterns.

Circadian rhythm of spontaneous non-linear peptidization with proteinogenic amino acids in abiotic solutions versus homochirality

In this short communication, we report on three striking phenomena of the circadian rhythm. One was observed with the non-linear concentration changes of the monomeric L-Cys and the non-linear yields of the L-Cys derived peptides, when undergoing spontaneous non-linear peptidization. The other one was observed with the binary L-Phe-L-Pro system, and the third one with L-Ser, D-Ser, and DL-Ser. So far, no analogous reports have been released on the circadian rhythm of the spontaneous non-linear peptidization of proteinogenic amino acids in a sterile abiotic environment (70% aqueous acetonitrile, or 70% aqueous methanol solutions). At the moment, we cannot find any rational explanation of this phenomenon, yet it seems highly probable that its origin is analogous to or even of a primordial nature for the circadian rhythm phenomena abundantly found in biological samples by other researchers. An experimentally established lack of the circadian rhythm with peptidization of the non-proteinogenic amino acid (D-Se...

Dynamics of Spontaneous Peptidization of l-, d- and dl-Serine in an Abiotic Solution as Investigated with Use of TLC-Densitometry and the Auxiliary Chromatographic Techniques.

From our earlier investigations, it comes out that proteinogenic amino acids can undergo spontaneous oscillatory reactions of chiral inversion and peptidization. l-Serine (l-Ser) is an important proteinogenic amino acid with many vital functions in human and mammalian organisms, e.g., it is responsible for good condition of the nervous cell membranes. It undergoes spontaneous oscillatory processes of chiral inversion and peptidization, and the goal of this study was to compare the dynamics of its peptidization with that of d-Ser and dl-Ser (racemate). The main analytical technique used in our experiment was TLC-densitometry, and the auxiliary chromatographic techniques were HPLC-evaporative light scattering detector and LC-MS. The results obtained witness to the differences in peptidization dynamics of the two Ser enantiomers (l and d) and of the racemic mixture thereof (dl). It was shown that dl-Ser characterizes with the higher, and l- and d-Ser with the lower peptidization yields.