Title Interakcija aminokiselina s kristalima oktakalcijevog fosfata Title (english) Interactions of amino acids with octacalcium phosphate crystals Author Sarah Mateša Mentor Davor Dolar (mentor)Committee member Davor Dolar (predsjednik povjerenstva)Committee member Jelena Macan (član povjerenstva)Committee member Maja Dutour Sikirić (član povjerenstva)Granter University of Zagreb Defense date and country 2017-09-29, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Kalcijevi fosfati (CaP) imaju važnu ulogu u biološkoj i patološkoj mineralizaciji te industrijskim procesima. Jedan od biološki najznačajnijih kalcijevih fosfata je oktakalcijev fosfat (OCP), koji je jedna od komponenti zubnih i bubrežnih kamenaca. Zbog svoje kristalne strukture i morfologije, OCP je pogodan model za proučavanje interakcija s aditivima u svrhu razumijevanja procesa biomineralizacije. U biomineralizaciji anorganske soli nastaju u dodiru s organskom matricom, koja se većim dijelom sastoji od proteina. Iako su osnovni principi interakcija proteina i kristala poznati, još nije jasna uloga pojedinih aminokiselina. Razjašnjenje uloga pojedinih aminokiselina omogućilo bi pripravu aditiva za dobivanje minerala željenih svojstava. Cilj ovoga rada bio je sintetizirati kristalno sjeme OCP-a i istražiti transformaciju dobivenih kristala u taložnim sustavima, u uvjetima sličnim fiziološkim (pH 7,4, temperatura 25 °C), u prisutnosti asparaginske kiseline, asparagina, poli(asparaginske kiseline) i lizina. Kristalno sjeme OCP je pripremljeno modificiranom metodom prema Boanini, na način da se u fosfatnu otopinu (c(Na2HPO4) = c(NaH2PO4·H2O) = 5 mmol dm^-3) dokapavala otopina kalcijevog acetata (c = 0,04 mol dm^-3), tijekom 2 h na 70 °C uz mehaničko miješanje. Kristalni rast i transformacija pripremljenih kristala u metastabilnoj otopini (c(CaCl2) = c(Na2HPO4) = 4,2 mmol dm^-3, c(NaCl) = 0,15 mol dm^-3, pH 7,4) u prisutnosti različitih koncentracija aminokiselina praćeni su potenciometrijski. Na temelju dobivenih pH krivulja određena su vremena u kojima je talog odijeljen i karakteriziran pomoću FTIR spektroskopije, pretražne elektronske mikroskopije i rendgenske difrakcije na prahu. Dobiveni rezultati pokazali su da je sintetizirano kristalno sjeme u obliku velikih igličastih pločastih kristala karakterističnih za OCP. Aminokiseline ovisno o koncentraciji u kojoj su prisutne utječu na brzinu transformacije OCP. Asparagin i lizin ne utječu na sastav i morfologiju taloga. Kao i u kontrolnom sustavu nakon 4 h gotovo je završena transformacija OCP u CaDHA. Rendgenogrami praha taloga nastalih nakon 4 h u prisutnosti asparaginske i poli(asparaginske) kiseline, ukazuju na mogući početak daljne transformacije CaDHA.
Abstract (english) Calcium phosphates (CaP) have an important role in biological and pathological mineralization and industrial processes. One of the biologically most important calcium phosphates is octacalcium phosphate (OCP), one of the components of dental and kidney stones. Because of its crystalline structure and morphology, OCP represents a suitable model system for studying the crystal – additive interactions with the aim to contribute to the understanding of biomineralization process. In the biological mineralization, inorganic salts are formed in the contact with organic matrix, which is mostly composed of proteins. Although the basic principles of protein and crystal interaction are known, the role of specific amino acids is still not clarified. Clarification of the role of individual amino acids would allow the preparation of tailored additives enabiling to obtain the minerals of desired properties. The aim of this research was to synthesize OCP seed crystals and investigate their transformation in conditions similar to the physiological (pH 7.4, temperature 25 °C), in the presence of aspartic acid, asparagine, polyaspartic acid and lysine The OCP seed, was prepared by a modified method according to Boanini by dropwise adding of calcium acetate solution (c = 0.04 mol dm^-3) in phosphate solution (c(Na2HPO4) = c(NaH2PO4·H2O) = 5 mmol dm^-3) for 2 hours at 70 °C with mechanical stirring. Crystal growth and transformation of OCP seed crystals in metastable solution (c(CaCl2) = c(Na2HPO4) = 4.2 mmol dm^-3, c(NaCl) = 0.15 mol dm^-3, pH 7.4) in the presence of different concentrations of aminoacids were followed potentiometrically. Precipitates were taken after different times determined based on pH curves and characterized by FTIR spectroscopy, scanning electron microscopy and powder X-ray diffraction. Obtained results have shown that the OCP seed crystals precipitate in the form of typical, big needle-shaped plate-like crystals. Amino acids affect the rate of OCP transformation, depending on the concentration in which they are present. Asparagine and lysine do not affect the composition and morphology of the precipitate. As in the control system after 4 hours, the OCP transformation in CaDHA is almost complete. Rendogenograms of powders formed after 4 hours in the presence of asparagine and polyaspartic acid indicate a possible beginning of further transformation of CaDHA.
Keywords
OCP
kristalno sjeme
kalcijevi fosfati
aminokiseline
Keywords (english)
OCP
crystal seed
calcium phosphates
amino acids
Language croatian URN:NBN urn:nbn:hr:149:250577 Study programme Title: Environmental Engineering - Graduate study Type of resource Text File origin Born digital Access conditions Closed access Terms of use Created on 2020-04-30 13:24:41
