Title Interakcije kristala kalcijevog hidrogenfosfata dihidrata s aminokiselinama Title (english) Interactions of calcium dihydrogenphosphate dihydrate crystals with amino acids Author Marina Kostešić Mentor Jelena Macan (mentor)Committee member Jelena Macan (predsjednik povjerenstva)Committee member Davor Dolar (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 važnijih kalcijevih fosfata je kalcijev hidrogenfosfat dihidrat (DCPD), koji se pojavljuje u bubrežnim kamencima i zubnom karijesu, te se primjenjuje u industrijskim procesima. Zbog svoje kristalne strukture, pogodan je model za proučavanje interakcija s aditivima u svrhu razumijevanja procesa biomineralizacije. U biomineralizaciji anorganske soli nastaju u dodiru s organskom matricom, koja se većim djelom sastoji od proteina. Iako su osnovni principi interakcija proteina i kristala poznati, još nije jasna uloga pojedinih aminokiselina. Razjašnjenje njihove uloge omogućilo bi pripravu aditiva za dobivanje minerala željenih svojstava. Aminokiseline su osnovne građevne jedinice proteina. Zajedničko obilježje svih aminokiselina jest prisutnost najmanje jedne amino skupine i jedne karboksilne skupine. Bočni lanac koji određuje strukturu aminokiselina označava se s R i različit je za svaku od aminokiselina. Cilj ovoga rada bio je sintetizirati kristalno sjeme DCPD-a i istražiti transformaciju dobivenih kristala u metastabilnoj otopini u uvjetima sličnim fiziološkim (pH 7,4, temperatura 25 °C), u prisutnosti asparaginske kiseline, asparagina i poli(asparaginske kiseline). DCPD je pripremljen brzim miješanjem jednakih volumena otopina kalcijevog hidroksida i fosforne kiseline uz magnetsko miješanje na (25 ± 0,1) °C. Kristalni rast i transformacija sintetiziranih 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. Dobiveni rezultati pokazali su da je sintetizirano kristalno sjeme u obliku velikih pločastih kristala karakterističnih za DCPD. U svim taložnim sustavima nakon 4 h, odnosno 5 h, nastaje kalcijev deficijentni hidroksiapatit (CaDHA). Aminokiseline ne utječu na sastav i morfologiju taloga, ali utječu na brzinu transformacije ovisno u koncentraciji u kojoj su prisutne u sustavu.
Abstract (english) Calcium phosphates (CaP) attract attention due to their role in the normal and pathological mineralization, as well as in industrial processes. Calcium hydrogenphosphate dihydrate (DCPD) is one of the major calcium phosphates minerals which can be found in kidney stones, dental caries and used in the industrial processes. Because of its crystal structure and morphology, DCPD represents a good model system for studying amino acids and crystals interactions in purpose of understanding mineralization 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 certain amino acids is still not clarified. Clarification of their role would allow the preparation of additives to obtain minerals of desired properties. Amino acids are the basic building blocks of proteins. A common feature of all amino acids is the presence of at least one amino group and one carboxyl group. The side chain of the amino acids, designated by R, is different for each of the amino acid and it determinates its structure. The aim of this research was to synthesize DCPD seed crystals and investigate the transformation of seed crystals in metastable solution in conditions similar to physiological ones (pH 7,4, temperature 25 °C), in the presence of aspartic acid, asparagine and polyaspartic acid. DCPD was prepared by rapid mixing of equal volumes of calcium hydroxide and phosphoric acid solutions. Systems were magneticaly stireed for 1 hour at (25 ± 0.1) °C. Crystal growth and transformation of DCPD 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 on pH curves and characterized by IR spectroscopy, X-ray diffraction and scanning electron microscopy. Obtained results have shown that the synthesized seed crystals occur in the form of big plate-like crystals typical for DCPD. In all precipitation systems after 4 or 5 hours, calcium defitient hydroxyapatite (CaDHA) precipitates. Aminoacids don't have an effect on structure and morphology of the precipitate, but they do have an influence on the rate of transformation, depending on concentration present in the system.
Keywords
DCPD
kristalno sjeme
kalcijevi fosfati
aminokiseline
Keywords (english)
DCPD
crystal seed
calcium phosphates
amino acids
Language croatian URN:NBN urn:nbn:hr:149:265553 Study programme Title: Chemical Engineering - Graduate study Type of resource Text File origin Born digital Access conditions Closed access Terms of use Created on 2020-04-30 13:00:01
