Dissociation of biomolecules in liquid environments during fast heavy-ion irradiation.

The effect of aqueous environment on fast heavy-ion radiation damage of biomolecules was studied by comparative experiments using liquid- and gas-phase amino acid targets. Three types of amino acids with different chemical structures were used: glycine, proline, and hydroxyproline. Ion-induced reaction products were analyzed by time-of-flight secondary-ion mass spectrometry. The results showed that fragments from the amino acids resulting from the C-Cα bond cleavage were the major products for both types of targets. For liquid-phase targets, specific products originating from chemical reactions in solutions were observed. Interestingly, multiple dissociated atomic fragments were negligible for the liquid-phase targets. We found that the ratio of multifragment to total fragment ion yields was approximately half of that for gas-phase targets. This finding agreed with the results of other studies on biomolecular cluster targets. It is concluded that the suppression of molecular multifragmentation is caused by the energy dispersion to numerous water molecules surrounding the biomolecular solutes.

Influencia de la radiación gamma como método de esterilización sobre el polímero poli VPAVG (Valina-Prolina-Alanina-Valina- Glicina) / Influence of gamma radiation as a sterilization method on polymer poli VPAVG (Valine- Proline- Alanine-Valine-Glicine)

El polímero poli (VPAVG) pertenece a la familia de materiales bioelásticos derivados de la elastina y ha demostrado poseer cualidades óptimas para la formación de sistemas de cesión controlada, así como una biocompatibilidad aceptable en determinados tejidos. Las formulaciones preparadas a partir del biomaterial deben ser estériles, si se pretende administrar por una vía que implique ruptura de barreras biológicas. Por lo anterior, resulta esencial conocer el comportamiento del polímero y sus formulaciones frente al proceso de esterilización empleado. El objetivo de este trabajo fue, por tanto, evaluar la influencia de la radiación gamma como método de esterilización sobre las ca - racterísticas físicas del poli (VPAVG) y de las partículas for - madas con éste. En cuanto al polímero, no se apreciaron diferencias en su apariencia física antes y después de la esterilización. Sin embargo, las partículas obtenidas a partir del poli (VPAVG) y posteriormente esterilizadas experimentaban cambios en su morfología. En cuanto al tamaño de las partículas, se determinó que las obtenidas con polímero esterilizado presentaban cierta tendencia a formar agregados de menor tamaño que los encontrados con el polímero sin esterilizar. Se concluyó que el biomaterial ensayado y las formulaciones eran susceptibles a las radiaciones gamma como método de esterilización final, proponiéndose recurrir a otro tratamiento que garantice su esterilidad final.

The poli polymer (VPAVG) belongs to the family of bioelastic materials derived from elastin, and it has showed the best qualities for the creation of systems of controlled cession, as well as an acceptable biocompatibility in certain tissues. If any preparation made from this biomaterial has to be administered in any way that implies the rupture of biological barriers, the preparation must be sterile. By this means, it is essential to know the behaviour of this polymer and its formulations, facing the sterilization process being used. The objective of this research was learn the influence of gamma radiation as a sterilization method over the physical characteristics of poli (VPAVG) and the particles formed by it. As the polymer, we did not observe any differences in physical appearance before and after sterilization. Particles formed by the polymer (VPAVG) and sterilized after, experimented changes in their morphology. As the size of the particles, we observed that those obtained with the sterilized polymer showed a tendency to form smaller aggregates than those found with the non-sterilized polymer. We concluded that the essayed biomaterial and its formulations were susceptible to gamma radiations as final sterilization method, proposing to use another treatment to guarantee the final sterile condition.

Synthesis and characterization of oligoproline-based molecular assemblies for light harvesting.

Helical oligoproline arrays provide a structurally well-defined environment for building photochemical energy conversion assemblies. The use of solid-phase peptide synthesis (SPPS) to prepare four such arrays, consisting of 16, 17, 18, and 19 amino acid residues, is described here. Each array contains the chromophore [Rub'(2)m](PF(6))(2) (b' = 4,4'-diethylamidocarbonyl-2,2'-bipyridine; m = 4-methyl-2,2'-dipyridine-4'-carboxylic acid) and the electron transfer donor PTZ (phenothiazine). The arrays differ systematically in the distance between the redox-active metal complex and PTZ sites. They have been used in photophysical studies to provide insight into the distance dependence of electron transfer. (J. Am. Chem. Soc. 2004, 126, 14506-14514). This work describes the synthesis, purification, and characterization of the oligoproline arrays, including a general procedure for the synthesis of related arrays.

Does irradiation affect the protein composition of saliva?

The purpose of this study was to compare the relative amount of low molecular weight salivary proteins in patients with head and neck tumours treated with radiotherapy and healthy subjects. Reverse-phase high-pressure liquid chromatography was used for protein separation. Nine protein fractions (including acidic and basic proline-rich proteins (PRPs), cystatins, histatins and statherin) were identified in saliva from irradiated patients as well as healthy subjects. However, compared with non-irradiated healthy subjects, the fraction of acidic PRPs was significantly reduced in irradiated patients. These data indicate an alteration of the relative amount of low molecular weight salivary proteins in irradiated patients besides the reduction of salivary flow.

The effect of preoperative radiotherapy on systemic collagen deposition and postoperative infective complications in rectal cancer patients.

PURPOSE: Preoperative, high-dose radiotherapy for rectal cancer reduces local recurrence rates and improves overall survival. However, adverse effects in varying degrees include impaired wound healing and local infection. This study investigates the influence of preoperative, high-dose radiotherapy on subcutaneous accumulation of collagen in a primary rectal cancer group operated on with or without adjuvant radiotherapy. METHODS: Forty-two eligible patients who underwent total mesorectal excision surgery with or without radiotherapy were included in the study. Polytetrafluoroethylene tubings were implanted in the arm ten days before surgery (three days before the start of radiotherapy). Implants were extracted the day before surgery. New implants were inserted before surgery and were extracted ten days after surgery. The hydroxyproline and proline contents of the implants were measured and the hydroxyproline/proline ratio was calculated as a measure for deposited collagen relative to protein. Blood loss, postoperative complications, and blood levels of hemoglobin, leukocytes, and albumin were recorded. RESULTS: The two groups were similar in relation to Dukes stage, age, and body mass index. Infectious complications developed in 39 percent of patients after radiotherapy compared with 16 percent in the nonirradiated group. In the irradiated patients with infective complications we found a significant decrease in the hydroxyproline/proline ratio compared with that of irradiated patients without infections (P = 0.037). There was a significant decrease in the leukocyte count preoperatively and postoperatively in the irradiated group compared with surgery alone. CONCLUSIONS: High-dose, short-term radiotherapy does not have a systemic effect on collagen accumulation, but a significant reduction is manifested in infected patients. Radiotherapy also impairs leukocyte production and increases the postoperative infective complication rate.

Effects of mutagenetic substitution of prolines on the rate of deprotonation and reprotonation of the Schiff base during the photocycle of bacteriorhodopsin.

Membrane-buried proline residues are found in many transport proteins. To study their roles in the structure and function of bacteriorhodopsin (bR), effects of the individual substitutions of Pro-50, Pro-91 and Pro-186 on the deprotonation and reprotonation kinetics of the Schiff base (SB) were determined by flash photolysis. The obtained rate constants and the amplitudes of the slow and fast components were compared with those of ebR (wild-type bR, the native protein that is expressed in Escherichia coli). The deprotonation rates of PSB were found to be 10 times faster than that of ebR for P50A, P91A and P91G mutants, and 4 times faster for the P50G mutant. These mutations also increased the initial reprotonation rate of the SB, although the overall change in the reprotonation rate is not as significant as that in the deprotonation rate. Our results indicate that Pro-50 and Pro-91, as well as Pro-186, are important for the proton-pumping function of bR.

[The question of amino acid isomerization in the microwave field. Results of a model study with standard solutions]. / Zur Frage der Aminosäureisomerisierung im Mikrowellenfeld. Ergebnisse eines Modellversuches mit Standardlösungen.

Aqueous standard-solutions of L-alanine, L-glutamic acid, and L-proline do not reveal any increase of D-enantiomers after 30 min heating--neither by the conventional method on a hotplate, nor in a standard microwave oven. A specific "microwave effect" and, hence, a special consumer risk is, in contrast to recent assumptions, not detectable. Effects on the amino acids which were observed in conventionally heated samples are explained by higher heat-exposure during the treatment of these samples.

Induction of proline prototrophs in CHO-K1 cells by heavy ions.

Using an established mammalian cell line, Chinese hamster ovary cells (CHO-K1), we have observed the induction of prototrophs by various heavy ions. This cell line requires proline for normal growth in medium with low serum concentration. X-rays, three types of heavy particles (600 MeV/u iron, 670 MeV/u neon, and 320 MeV/u silicon ions), ethylmethane sulphonate and 5-azacytidine were used to induce revertants which were proline independent. Log-phase cells treated with 5-azacytidine showed a very high reversion frequency. The induction frequency per viable cell appears to be dose dependent for these four types of radiation, and the dose-response curves are approximately linear. Our results also indicate that the effectiveness of high-LET particles in inducing proline prototrophs is much greater than that of low-LET radiation. The RBE value for the induction of prototrophs was calculated for neon, silicon, and iron particles and found to be about 1.3, 1.7 and 4.5, respectively. At equal survival level, the reversion frequency for X-rays and EMS was about the same.

E.S.R. of spin-trapped radicals in gamma-irradiated polycrystalline amino acids. Chromatographic separation of radicals.

The free radicals produced by gamma-radiolysis of polycrystalline amino acids (L-valine, L-leucine, L-isoleucine and L-proline) at room temperature in the absence of air were investigated by spin trapping with 2-methyl-2-nitrosopropane (MNP). The spin adducts produced by dissolving the irradiated solids in aqueous MNP solutions were separated by high-performance liquid chromatography and then identified by e.s.r. Deamination (ring-opening reaction for L-proline) was observed for all amino acid. For L-valine and L-leucine, H-abstraction from the tertiary carbon in the side chains occurred. For isoleucine, H-abstractions from the alpha-carbon of the amino acid and from a non-terminal carbon in the side chain were found.

Gamma-radiolysis of aqueous solution of proline.

Gamma-radiolysis of 0.05 M neutral proline solution was investigated. As the main reaction of proline radiolysis in oxygenated solutions, the hydroxylation reactions leading to hydroxyproline formation and the reactions leading to the total destruction of the pyrrolidine ring were shown. In oxygen-free solutions the yield of these reactions decreased; in this medium combination reactions giving rise to higher molecular weight combination products (up to approx. 1500) belong to the most important ones. In addition to radiation-decarboxylation reactions the products of radiation-carboxylation reactions were also detected in the irradiated solution of proline free of oxygen.