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Molekule 1,2-dipalmitoil-sn-glicero-3-fosfokolina (engl. 1,2-dipalmitoyl-sn-glicero-3- phosphatidylcholine, DPPC) u vodenom mediju stvaraju hidrirane dvosloje koji se, ovisno o temperaturi, nalaze u određenoj fazi. Prijelaz DPPC-a iz faze gela (Lβ') u fazu fluida (Lα), odnosno glavni fazni prijelaz opažen pri temperaturi mekšanja (Tm), prekinut je valovitom fazom (Pβ') koja se opaža pri temperaturi pretprijelaza (Tp). Budući da su Tm i Tp iznimno osjetljive na ugradnju organskih molekula u lipidni dvosloj, posebice onih koje su kadre primati i otpuštati proton, u sklopu ovog diplomskog rada istraženi su višestruki hidrirani dvosloji DPPC lipida u odsutnosti i prisutnosti male količine palmitinske kiseline (engl. palmitic acid, PA) u puferima različitih pH vrijednosti. Tm i Tp određene su analizom vibracijskih potpisa metilenskih (νsCH2) i fosfatnih (νasPO2−) skupina iz temperaturno-ovisnih FT-IR spektara. Dobiveni podaci su djelomično upotpunjeni onima dobivenima iz razlikovno-pretražne kalorimetrije (engl. differential scanning calorimetry, DSC). 1,2-dipalmitoyl-sn-glycero-3-phosphocoline form hydrated bilayers in an aqueous medium which, depending on the temperature, can be found in certain phase. The transition from gel (Lβ') to fluid phase (Lα), assigned as the main phase transition with a peak at melting point temperature (Tm), is interrupted by the ripple phase (Pβ') observed at the pretransition temeprature (Tp). Since Tm and Tp are extremely sensitive to the incorporation of organic molecules into the lipid bilayer, especially those capable of receiving and releasing a proton, multiple hydrated bilayers of DPPC lipids in the absence and presence of small amounts of palmitic acid (PA) in buffers of different pH values have been investigated across this thesis. Tm and Tp have been determined by the analysis of vibrational signatures of methylene (νsCH2) and phosphate (νasPO2−) groups from temperature-dependent FT-IR spectra. These data have been partially supplemented by those obtained from differential scanning calorimetry (DSC).

Proton transfer along biological interfaces is exceptionally difficult to unravel from both experimental and theoretical perspective [1]. In addition to rather scarce computational studies, experimental endeavours are mostly focused on the incorporation of membrane- anchored pH-sensitive dyes that detect the arrival of a migrating proton. Evidently, the establishment of a probe-free method would serve as considerable breakthrough in deepening our knowledge on lateral proton transfer. In this regard, we have examined lipid multibilayers of 1, 2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) in the absence and the presence of small amount of palmitic acid (PA) (2 %) in buffers of pH values 4 ≤ pH ≤ 9 by FT- IR spectroscopy. Depending on the pH value, PA can be protonated (COOH) or deprotonated (COO−) and, consequently, placed at different depth of a lipid bilayer [3]. The presence of such small amount of PA should not significantly modify characteristic undulations of DPPC multibilayers surface [4], but accompanying proton transfer is expected to leave its signature. The latter are indirectly detected by FT-IR spectroscopy coupled with MCR-ALS with EFA analysis (Fig. 1) that is very sensitive and powerful tool in discerning of coupled events [5]. Experimental observations are corroborated by molecular dynamics (MD) simulations and calorimetric measurements.

Molekule 1, 2-dipalmitoil-sn-glicero-3- fosfokolina (engl. 1, 2-dipalmitoyl-sn-glicero- 3- phosphatidylcholine, DPPC) u vodenom mediju stvaraju hidrirane dvosloje koji se, ovisno o temperaturi, nalaze u određenoj fazi. Prijelaz DPPC-a iz faze gela (Lβ') u fazu fluida (Lα), odnosno glavni fazni prijelaz opažen pri temperaturi mekšanja (Tm), prekinut je valovitom fazom (Pβ') koja se opaža pri temperaturi pretprijelaza (Tp). Budući da su Tm i Tp iznimno osjetljive na ugradnju organskih molekula u lipidni dvosloj, posebice onih koje su kadre primati i otpuštati proton, u sklopu ovog diplomskog rada istraženi su višestruki hidrirani dvosloji DPPC lipida u odsustvu i prisustvu male količine palmitinske kiseline (engl. palmitic acid, PA) u puferima različitih pH vrijednosti. Tm i Tp odredit će se analizom vibracijskih potpisa metilenskih (νsCH2) i fosfatnih (νasPO2−) skupina iz temperaturno- ovisnih FT-IR spektara. Dobiveni podaci će se djelomično upotpuniti onima dobivenima iz razlikovno-pretražne kalorimetrije (engl. differential scanning calorimetry, DSC).

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2).

U ovom radu je opisano ispitivanje elektrokemijskih svojstava rutina (3`, 4`, 5, 7- tetrahidroksiflavon-3beta-D-rutinozida) u tri različita inertna elektrolita: KCl, NaCl i LiCl. Mjerenja su izvedena pomoću diferencijalne pulsne voltametrije. Iz voltamograma je vidljivo da struja i potencijal oksidacijskih strujnih vrhova rastu s porastom koncentracije rutina. Najbolji kalibracijski dijagram je dobiven u otopini s kalijevim kloridom kao inertnim elektrolitom, pa je za određivanje nepoznate koncentracije rutina u ekstraktu kore jabuke Zimnjare korišten taj kalibracijski dijagram. Određena koncentracija rutina u ispitivanom ekstraktu iznosi 18, 7∙10-6 mol dm-3.

The aim of this study was to examine electrochemical properties of rutin (a flavonoid widely distributed in fruits and vegetables, e.g. apples, buckwheat, green tea, aronia berries etc.) in three different electrolytes (KCl, NaCl, LiCl) by cyclic and differential pulse voltammetry (Ic = 0.34 mol dm-3). Measurements were conducted in a three electrode voltammetric cell in an aqueous media. Glassy carbon was used as a working electrode, platinum wire as counter electrode and Ag/AgCl electrode as a reference electrode. Inert atmosphere was acomplished by system purging with high purity argon Ar 5 (Ar = 99.999 %), before each measurement. Cyclic voltammograms of rutin revealed two oxidation peaks in all three electrolytes, which were associated with oxidation of four - OH groups of quercetin. The first oxidation peak was reversible and it corresponds to the oxidation of the 3`, 4`- dihydroxy groups on the B-ring of rutin and the second oxidation peak was irreversible and it corresponds to oxidation of 5, 7-dihydroxy groups on the A-ring of rutin. Differential pulse voltammograms also revealed two oxidation peaks. Linear dependence of Ip vs. rutin concentration was found in all three electrolytes. The best calibration diagram was obtained in 0.34 mol dm-3 KCl solution in rutin concentration range from 1.0∙10-6 mol dm-3 to 4.2∙10-5 mol dm-3