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Macrozones are new conjugates of azithromycin and thiosemicarbazones, which exhibit very good in vitro antibacterial activities against susceptible and some resistant bacterial strains thus showing a potential for further development. In this work, we applied a combination of NMR and fluorometric methods to study interactions of bioactive macrozones with their biological targets: bovine serum albumin and ribosome isolated from Escherichia coli. Saturation transfer difference (STD) and water-ligand observed via gradient spectroscopy (WaterLOGSY) spectra provided valuable data on ligand orientation, solvent exposure, binding epitopes and specificity. The binding stoichiometry and association constants were calculated from fluorometric data. These results can serve as a good starting point for the design of new macrozones and their metal complexes with improved bioactivity.

Značajan porast bakterijske rezistencije utječe na sve veću potrebu za istraživanjem i razvojem novih antibiotika. U sklopu ovog rada pripravljene su tri nove klase makrozona, konjugata makrolidnog antibiotika azitromicina i tiosemikarbazona. Tiosemikarbazoni su korišteni za kemijsku modifikaciju azitromicina na tri različita položaja. Cilj rada je priprava novih derivata makrolida sa širim spektrom biološke aktivnosti. Pripravljenim spojevima određena je biološka aktivnost in vitro na susceptibilne i rezistentne Gram-pozitivne i Gram-negativne bakterije te su istražene interakcije s biološkim receptorima. Za proučavanje interakcija primijenjena je spektroskopija NMR, cirkularni dikroizam, fluorescencijska spektroskopija i molekulsko modeliranje. Makrozoni su pokazali zadovoljavajuću biološku aktivnost, posebice na neke rezistentne bakterijske sojeve na koje azitromicin nije aktivan. Rezultati dobiveni spektroskopskim metodama i molekulskim modeliranjem ukazuju na odnos strukture i aktivnosti novih derivata azitromicina, što može poslužiti za dizajn i otkriće biaktivnijih derivata makrolida. Owing to a significant increase in bacterial resistance, a high need for discovery and development of new antibiotics has emerged. As part of this work, three novel classes of macrozones, conjugates of macrolide antibiotic azithromycin and thiosemicarbazones, were prepared. Thiosemicarbazones were used to chemically modify azithromycin at three different positions. The aim of this thesis was to prepare compounds with a wider range of biological activity including resistant bacterial strains. In vitro biological activity of the prepared compounds was determined against susceptible and resistant Gram-positive and Gram-negative bacteria, and interactions with biological receptors were investigated. Macrozones showed satisfactory biological activity, especially against some resistant bacterial strains to which azithromycin is inactive. NMR spectroscopy, circular dichroism, fluorescence spectroscopy, and molecular modeling were further used to study interactions of selected compounds with biological targets. The results obtained by spectroscopic methods and molecular modeling indicate a relationship between structure and activity of new azithromycin derivatives, which can be used for design and discovery of more active macrolide derivatives.

Owing to their high efficacy and safety, macrolides have been in widespread clinical use for the treatment of upper and lower respiratory tract infections. The reversible binding of macrolides to the 23S rRNA of the large ribosomal subunit, at or near the peptidyl transferase center, blocks the exiting tunnel for newly synthesized peptides and thus inhibits the synthesis of bacterial proteins. The chemical structure of clinically relevant macrolides is characterized by a macrolactone ring, usually consisting of 14–16 atoms, substituted by polar and non-polar groups and linked to one or more carbohydrate units via glycosidic bonds. Despite the fact that new antibiotics have been developed, some bacteria have acquired broad resistance, representing a global medical problem which can only be resolved by the discovery of new and more potent drugs. Our previous studies have shown that linking known macrolide antibiotics to bioactive thiosemicarbazones resulted with novel conjugates, the macrozones, efficient against multidrug resistant strains. It has also been reported that some thiosemicarbazones and their metal complexes possess anti-infective, anti-tumor and anti inflammatory activities. In this work, we studied the interactions of new bioactive macrolide conjugates and their metal complexes with the Escherichia coli ribosome by a combined use of NMR spectroscopy, fluorescence measurements and molecular modelling simulations. Saturation transfer difference (STD), WaterLogsy and transferred nuclear Overhauser effect (trNOE) NMR experiments provided valuable data about ligand conformations and binding epitopes. Fluorescence spectra were further processed by multivariate data analysis methods to assess binding constants. Molecular modelling simulations revealed the macrolide binding sites at the E. coli ribosome. The obtained results can further be exploited in the process of designing novel macrolide derivatives with activity against resistant pathogens.

Macrolides belong to the largest class of antibiotics and are clinically used for the treatment of upper and lower respiratory tract infections. They inhibit the synthesis of bacterial proteins by reversible binding to the ribosomal 23S RNA at the peptidyl transferase region, which blocks the exiting tunnel for newly synthesized peptides. Despite the fact that new antibiotics have recently been developed, some bacteria have acquired broad resistance, representing a global medical problem, which can only be resolved by the discovery of novel and more potent drugs. It has been reported that linking known macrolides to bioactive thiosemicarbazones resulted with new conjugates, the macrozones, efficient against multidrug resistant strains. On the other hand, some thiosemicarbazones and their metal complexes showed anti-infective, antitumor and anti- inflammatory activity. In this work, we structurally characterized several azithromycin- derived macrozones and their metal complexes. Furthermore, interactions between the macrozones showing excellent in vitro activity and the E. coli ribosome were studied by a combination of NMR methods and fluorescence measurements. Transferred nuclear Overhauser effect (trNOE), saturation transfer difference (STD) and WaterLogsy experiments provided a wealth of information about ligand conformations and binding epitopes. Fluorescence measurements revealed binding constants. The obtained results can serve as a good basis for the design and development of macrolide conjugates with enhanced biological properties.

Macrozones, i.e. thiosemicarbazone azithromycin derivatives, are a novel hybrid class of potential anti-infective macrolide compounds (Figure 1.a). [1] It has been well established that complexation of transition metals by the thiosemicarbazone moiety increases antibacterial activity of such ligand.[1] Therefore, we investigated the effect of nickel(II) complexation of macrozones on their antibacterial activity. Nickel(II) complexes of several thiosemicarbazones with 4-formylbenzoic and 3-formylsalicylic acid were prepared and structurally characterized via NMR spectroscopy and single-crystal X-ray diffraction (Figure 1.b). Nickel complexes were then coupled to the 4’’- aminopropyl azithromycin derivative, and the nickel(II) macrozone complexes were characterized using NMR spectroscopy and MS spectrometry. Prepared compounds were screened against a panel of selected Gram-positive and Gram-negative bacterial strains

Početak samog osiguranja seže daleko u prošlost, a do danas se razvila do najmanjih detalja prvobitno da bi zaštitila svoje korisnike pa i njene davaoce. Mnogobrojni trgovci, trgovine i trgovački lanci u svom poslovanju se susreću s raznim vrstama osiguranja. U današnje vrijeme trgovcima su rad i poslovanje olakšani velikim izborom pravog osiguranja za njihovo poslovanje. Osiguranje imovine i zaposlenika trgovcu nudi sigurnije poslovanje. Zaposleniku mirovinsko i zdravstveno osiguranje nudi sigurnost u sadašnjosti i budućnosti za sebe i za članove svoje obitelji. U ovom radu upoznajemo se s vrstama osiguranja potrebnih trgovačkom poduzeću za poslovanje u skladu sa zakonima Republike Hrvatske. Upoznati ćemo se s poslodavcem Tommy d.o.o. njegovom poviješću i sadašnjim stanjem poslovanja te osiguranjima koja mu pomažu poslovanje održati na visokom položaju., The origin of insurance itself dates far back into the past, and nowadays it has developed to the smallest details, mainly to protect its clients as well as its providers. Numerous vendors, markets and chain stores encounter various types of insurance in their business activities. Today, work and trade are facilitated with a wide range of perfect insurance for their conduct. Property and employee insurance offers a safer conduct of business to the trader, and retirement and health insurance offers stability in the present as well as in the future to the employee and their family. In this paper we will encounter types of insurance required for a commercial enterprise to conduct business in compliance with the laws of the Republic of Croatia. We will familiarise ourselves with the employer of Tommy d.o.o., its history and the current state of business as well as the insurances that help maintain its operations at a high position.

Azithromycin is a 15-membered macrolide antibiotic, clinically used for the treatment of upper and lower respiratory tract infections. Despite the fact that new macrolide classes have recently been developed, some bacteria have acquired broad resistance, representing a global medical problem. One of the most effective methods to combat resistance is based on a combinational approach, allowing synergistic interactions between antibiotics and other bioactive molecules. In respect to that, linking known macrolide antibiotics to bioactive thiosemicarbazone derivatives has increased efficacy and resulted in conjugates (macrozones) active against resistant strains. Aminopropyl derivatives of azithromycin are precursors for the macrozone synthesis. In this study, they have been structurally characterized in solution and solid state by NMR spectroscopy and MS spectrometry. The obtained structural and conformational data can serve as the basis for the design of new macrolide conjugates.

Macrozones are novel, bioactive macrolide derivatives, conjugates of azithromycin and thiosemicarbazone. Macrolides, such as azithromycin are group of antibiotics which are active against Gram positive and some Gram negative bacteria. They exert their biological activity by binding to the 50S ribosome subunit. Due to the frequent and improper use of drugs bacterial resistance has emerged. There is a need to discover new, more effective antibiotics. In this work, three classes of macrozones were synthesized and characterized by NMR spectroscopy. In order to investigate mechanisms of macrozones activity, interactions with E. Coli ribosome were studied by trNOESY and STD NMR methods. Since 3D structure plays a significant role in bioactivity, free and bound state conformations of macrozones were also investigated. These results should contribute to discover and design new compounds with improved antibacterial activity.

Macrolides represent a group of antibiotics whose structure is characterized by a macrocyclic lactone ring linked to one or more sugars. Macrolides are bacteriostatic antibiotics, they bind to the 50S subunit of the bacterial ribosome and thus inhibit synthesis of proteins essential for the growth of bacteria. They are effective against Gram-positive and some Gram-negative bacteria. Azithromycin is a semi-synthetic derivative of erythromycin A and belongs to the group of azalides, 15-membered macrolide antibiotics. Azithromycin has excellent pharmacokinetic properties and demonstrates satisfactory biological activity. However, bacterial resistance has emerged due to the frequent use of drugs and there is a need to discover new, more effective antibiotics. As part of this study, macrozones (novel conjugates of azithromycin and thiosemicarbazone) were successfully prepared. Since thiosemicarbazones exhibit antitumor and antibacterial activity, they were used to chemically modify azithromycin at three different positions. Structure and biological activity of macrozones against susceptible and resistant bacterial strains were determined. They showed very good activities against susceptible S. pneumoniae, S. pyogenes and E. faecalis strains, and excellent activity against resistant S. pneumoniae and S. aureus strains. NMR spectroscopy was used to study interactions of prepared compounds with ribosome and to determine the binding epitopes.

Azithromycin belongs to macrolide class of antibiotics wich exert its biological activity by binding to bacterial ribosome at or near the peptidyl transferase center thus inhibiting protein biosynthesis. They are effective in treating infections caused by Gram-positive and some Gram-negative bacteria. Due to the increased development of bacterial resistance much effort is directed towards the discovery of new more potent antibiotics. A series of bioactive azithromycin derivatives, the new class of macrozones have been prepared by coupling thiosemicarbazones to azithromycin at position 4" (Figure 1). Here we present their synthesis, characterization and interactions of macrozone precursor, 4"-aminopropyl azithromycin with the ribosome isolated from E. Coli. A combination of NMR experiments such as saturation transfer difference (STD) and transferred nuclear Overhauser effect spectroscopy (trNOESY) and molecular modeling were applied to determine binding epitopes and explore bound conformations.

Makrolidi su skupina antibiotika koji se koriste za liječenje infekcija uzrokovanih Gram-pozitivnim i Gram-negativnim bakterijama.1 Pripadaju skupini bakteriostatika, vežu se za podjedinicu bakterijskog ribosoma 50S i tako inhibiraju sintezu proteina. Jedan od najpoznatijih predstavnika makrolida jest azitromicin, polusintetski derivat eritromicina A, prvog izoliranog makrolida. Azitromicin je antibiotik širokog spektra djelovanja, te je posebice djelotvoran u liječenju bolesti koje zahvaćaju respiratorni sustav. Međutim, zbog sve većeg porasta broja rezistentnih patogenih mikroorganizama potrebno je istražiti i pripraviti nove derivate makrolida koji će pokazati širu biološku aktivnost.2, 3 Makrozoni su novi konjugati azitromicina i tiosemikarbazona koji pokazuju obećavajuću in vitro antibakterijsku aktivnost. Ovaj rad obuhvaća pripravu novih makrozonskih derivata makrolidnog antibiotika azitromicina u položaju 4" (slika 1), njihovu identifikaciju i strukturnu karakterizaciju. U tu svrhu koristile su se analitičke i spektroskopske metode: tekućinska kromatografija visoke djelotvornosti, nuklearna magnetna rezonancija i spektrometrija masa.

Due to a global problem of growing bacterial resistance, discovery of new antibiotics is of an outmost importance and various studies are in progress to overcome the resistance mechanisms.[1- 3] Macrozones are novel bioactive conjugates of azithromycin and thiosemicarbazides that posses very good in vitro antibacterial activity against selected Gram-positive and Gram-negative bacteria. [4] Efficient and rapid purification and isolation of newly synthesized bioactive compounds is a crucial step prior to biological evaluation. Furthermore, isolation and identification of impurities is very important procedure during the drug development in pharmaceutical industry. Preparative and semipreparative HPLC techniques are classical purification methods, but they can be time and solvent consuming. In this study we have successfully used hyphenated LC-SPE/NMR approach for the isolation and structural characterization of main components and some impurities in 9a- and 4''- tetrahydrofurfuryl macrozone reaction mixtures. Structures of the isolated compounds were proposed on the basis of the analysed one- and two-dimensional NMR spectra and MS spectra, respectively.

Macrolide antibiotics, such as azithromycin have been widely used to treat infections of both gram- positive and gram-negative bacteria. They exert their biological activity by binding to bacterial ribosome at or near the peptidyl transferase center thus inhibiting protein biosynthesis. Emerging multi-drug resistant microbial pathogens present today a serious and challenging problem in medical treatment which demands novel antimicrobial agents to be obtained. In order to discover and design more effective macrolide compounds, it is important to explore the interactions with ribosome and other biological targets and to elucidate and characterize bound conformations in solution. We have prepared a series of bioactive azithromycin conjugates, the macrozones, by coupling thiosemicarbazones to azithromycin. Here we present results of interaction studies of a selected macrozone and ribosome isolated from E. Coli. We used a combination of NMR experiments such as transferred nuclear Overhauser effect spectroscopy (trNOESY) and saturation transfer difference (STD) and molecular modeling to characterize binding epitopes and asses bound conformations.

Asphaltenes are complex and the most polar oil components with molecular weights estimated between 500 and 1000 Da which are soluble in benzene and toluene. The structure of asphaltenes and the elemental composition depend on origin, source rocks, depositional environment, diagenetic and thermal history. Asphaltenes contain condensed aromatic and saturated rings, aliphatic moieties, and some heteroatoms. They also contain metals, such as nickel, iron and vanadium. Asphaltenes may aggregate and precipitate during the downstream and upstream processes and cause many serious problems in production, refining and transportation. We will present here the results of aggregation study of asphaltenes isolated from the heavy crude oil (C) atmospheric (AR) and vacuum residues (VR). Asphaltenes were isolated from crude oil samples according to the standard method. The influence of metals, such as vanadium, nickel and iron on asphaltene aggregation have also been explored. DOSY NMR technique was applied to separate components from crude oils according to their diffusion coefficients. DOSY is a pseudo two-dimensional NMR experiment in which proton chemical shifts represent one dimension and translational diffusion coefficients represent another one. NMR signals of different species were separated according to their diffusion coefficients.

Macrolide antibiotics, such as azithromycin, have been widely prescribed for the treatment of respiratory tract infections owing to their high efficacy and safety.[1] Azithromycin belongs to an azalide subclass of 15-membered macrolide antibiotics. Emerging multi-drug resistant microbial pathogens present today a serious and challenging global problem which demands novel and more effective antimicrobial agents to be discovered. Thiosemicarbazones and some of their metal complexes have been shown to possess anti- infective, anti-inflammatory and antitumor activities. Some thiosemicarbazones have proven very useful to treat infections, such as the new antibiotics perchlozone and thiacetazone, which are good new agents against tuberculosis.[2] Our earlier experiments which included synthesis and biological and structural characterization of some macrolide conjugates showed that those hybrid compounds exhibited good activity against some resistant bacterial strains.[3-4] Here, we present synthesis and characterization of novel macrolide conjugates, the macrozones by linking azithromycin and some selected thiosemicarbazones.

Azithromycin is the most widely used broad- spectrum antibiotic due to it's exceptional therapeutic properties.[1] Despite to this fact, an increasing number of antibiotic- resistant bacteria demands more effective antimicrobial agents to be synthesized.[2] Third generation of macrolide antibiotics still lacks activity against some Gram-negative bacterial strains, especially against respiratory tract pathogens. In order to improve antibacterial activity, new synthetic approaches were described in the literature.[3] Conjugation of the azithromycin analogue, 9a- (γ-aminopropyl) derivative, and thiosemicarbazide moieties resulted in novel compounds, macrozones, which showed good in vitro activity against selected Gram positive and Gram negative bacterial strains. Preparative and semi-preparative liquid chromatography are classical methods for purification and isolation of the final product, but they are time and solvent consuming. Modern hyphenated NMR techniques, such as LC-SPE/cryoNMR, are much faster, more efficient and more sensitive tool for the isolation and identification of the reaction mixture components. [4, 5] In this study LC- SPE/cryoNMR technique was used for the isolation of a novel ethyl-phenyl macrozone and for impurity profiling of the reaction mixture.

Azithromycin belongs to an azalide subclass of 15- membered macrolide antibiotics. With a much improved pharmacokinetic and therapeutic properties over erythromycin, azithromycin became the most widely used broad-spectrum antibiotic. [1] An increasing number of antibiotic-resistant bacteria, especially respiratory tract pathogens, demand a more effective antimicrobial agents to be synthesized.[2] Thiosemicarbazones belong to a large group of thiourea derivatives and are well known as antibacterial, antiviral, anti- inflammatory, antifungal and anticancer therapeutics.[3] Conjugation of the azithromycin analogue, 9a- (γ-aminopropyl) derivative, and thiosemicarbazone moieties resulted in novel compounds, macrozones, which showed good in vitro activity against selected Gram positive and Gram negative bacterial strains. Modern approach to the impurity profiling of bioactive compounds is based on the use of hyphenated systems, such as LC-NMR and/or LC- MS.[4-6] One of the most efficient and powerful tools for on-line isolation and identification of compounds in complex mixtures in the pharmaceutical industry is the LC-SPE-NMR system.[6-7] In this study, LC-SPE/NMR technique was used for impurity profiling of the novel macrozones.

Canine babesiosis is an important tick-borne disease with worldwide distribution, caused by parasites of the Babesia genus.[1] Acute renal failure is one of the most common complication in canine babesiosis, which could result in decrease of glomerular filtration, and consequently developing azotemia and uremia.[2] The main goal of early diagnosis of renal disease and renal failure in dogs is to apply the therapy as soon as possible to slow or halt disease progression. Current conventional diagnostic tests of kidney damage in blood are widely used for diagnosis and monitoring of kidney disease.[3] However, they all have important limitations, such as serum creatinine concentration will only be increased when already 75 % of functional renal mass is lost.[4] Blood contains multitude, unstudied, and unknown biomarkers. Hence, analysis of metabolites represents a sensitive measure of biological status in health or disease, respectively the analyses of metabolites are essential to the understanding of biological systems and the mechanism of disease progression. The basic analytical technique for metabolomics analysis is nuclear magnetic resonance (NMR) spectroscopy. The goal of the research was to examine the differences of serum metabolom between dogs infected with B. canis and healthy dogs using NMR spectroscopy. Serum samples were collected from 4 dogs of various breeds and sex with naturally occurring babesiosis caused by B. canis, admitted to Faculty of Veterinary Medicine. Blood was collected at the admission day. Serum was also collected from 4 healthy dogs. Dogs with babesiosis was non-azotemic (serum creatinine < 140 μmol/L) with UPC > 0.5. Our preliminary results confirm that NMR is good platform for investigation of biomarkers in babesiosis.

Asphaltenes, the heaviest, the most polar and the least reactive molecules in crude oil can aggregate and cause many problems during oil recovery and refining process. Asphaltenes isolated from the Middle East crude oil, atmospheric and vacuum residues were studied in this work. It will be demonstrated that asphaltene aggregates form different molecular weight species with different composition and number of monomer units. Furthermore, aggregation process has been found to be affected by the magnetic field [1]. A significant increase of diffusion coefficients of aggregates upon the increase of the magnetic field strength will be shown and discussed in terms of higher molecular mobility of present species at higher magnetic fields that could lead to a degradation of aggregates. References [1] J. Parlov Vuković, P. Novak, T. Jednačak, M. Kveštak, D. Kovačević, V. Smrečki, I. Mikulandra, S. Glanzer, K. Zangger, J. Dispers. Sci. Technol. 40 (2019) DOI:10.1080/01932691.2018.1561302

Azithromycin belongs to an azalide subclass of 15- membered macrolide antibiotics. It was synthesized in the early 1980s as a semi- synthetic derivative of erythromycin.[1] With a much improved pharmacokinetic properties over erythromycin, azithromycin became the most widely used broad- spectrum antibiotic.[2] Thiosemicarbazones belong to a large group of thiourea derivatives and are well known as antibacterial, antiviral, anti- inflammatory, antifungal and anticancer therapeutics.[3] Furthermore, a new multi- functional thiosemicarbazones were designed to treat Alzheimer and malaria.[4, 5] Conjugation of the azithromycin and thiosemicarbazone derivatives resulted in novel compounds which showed good activity against some Gram positive and Gram negative bacterial strains. Modern approach to the drug impurity profiling is based on the use of hyphenated systems, such as LC-NMR and/or LC-MS. [6] One of the most efficient and powerful tools for on-line isolation and identification of compounds in complex mixtures in the pharmaceutical industry is the LC-SPE- NMR system. In this study, LC- SPE/CRYO NMR technique was used for impurity profiling of novel azithromycin conjugates.

Asfalteni predstavljaju najteže, najmanje reaktivne i najpolarnije frakcije sirove nafte. Sastoje se od aromatskih molekula supstituiranih alifatskim lancima, heteroatomima N, S i O te metala u tragovima, poput V, Ni i Fe. Ove kompleksne makromolekule sklone su stvaranju agregata, što uzrokuje poteškoće prilikom proizvodnje i transporta nafte. Agregacija asfaltena iz vakuumskog ostatka sirove nafte je u ovome radu proučavana spektroskopijom NMR korištenjem tehnika inverznog oporavka i DOSY NMR. OdreĎeno je koncentracijsko područje u kojem nastaju agregati u toluenu te je istražen utjecaj porfirina vanadija(IV), nikla(II) i željeza(III) na vrijednosti difuzijskih koeficijenata, relaksaciju i agregaciju asfaltena. Nakon dodatka porfirina nije zapažen utjecaj na difuzijske koeficijente i agregaciju, dok je izmjereno značajno smanjenje longitudinalnog vremena relaksacije jezgre 1H zbog paramagnetnog doprinosa metala. Na temelju izmjerenih difuzijskih koeficijenata izračunati su hidrodinamički radijusi i molekulske mase monomera i agregata asfaltena. Očekuje se da će dobiveni rezultati pridonijeti boljem razumijevanju procesa agregacije ovih spojeva. Aspahltenes represent the heaviest, least reactive and most polar fraction of crude oil. They consist of aromatic molecules substituted by aliphatic chains, heteroatoms N, S and O and trace amounts of metals, such as Ni, V and Fe. These complex macromolecules tend to form aggregates causing many problems in crude oil production and transportation. In this reserch, aggregation behavior of asphaltenes obtained from vaccum residue of crude oil distillation was investigated by applying inversion recovery and DOSY NMR techniques. The lowest aggregation concentration in toluene was determined and the influence of V(IV), Ni(II) and Fe(III) porphyrins on diffusion coefficient, relaxation and aggregation process was studied. The addition of metalloporphyrins significantly decreased longitudinal relaxation time due to the paramagnetic contribution, but no effect on diffusion coefficient was observed in used concentration range. Hydrodynamic radii and molecular weights of the studied compounds were calculated from their diffusion coefficients. It is expected that the presented results will contribute to better understanding the asphaltene aggregation process.

Asphaltenes are the heaviest, most polar and least reactive molecules in crude oil, primarily consisting of carbons and hydrogens, some heteroatoms, such as sulfur, nitrogen, oxygen and traces of transition metals. They may aggregate during the downstream and upstream processes and cause many problems in production, refining and transportation. Asphaltene aggregation highly depends on the chemical nature of the crude oil, temperature and pressure. In this research, concentration dependent diffusion measurements were carried out to determine the lowest aggregation concentration of Middle Eastern asphaltenes and to study how the addition of V(IV), Fe(III) and Ni(II) affects the aggregation process. Asphaltene components were separated by DOSY NMR technique according to their diffusion properties. The influence of T1 relaxation on average diffusion coefficients was investigated by inversion recovery experiments. Changes in diffusion coefficients reflected the formation of different asphaltene types. It is expected that the presented results could throw more light into the asphaltene aggregation mechanism.

Nitrili su organski spojevi, široko rasprostranjeni u prirodi, sintetskim materijalima te lijekovima. Nitrili se mogu sintetizirati u laboratoriju te izolirati iz prirodnih materijala. U uvodu su navedena pravila imenovanja nitrila te osnovna fizikalna i kemijska svojstva. Nakon uvoda, u poglavlju Priprava nitrila opisane su neke laboratorijske i industrijske metode za sintezu odgovarajućih nitrila. Obrađene su sljedeće metode: cijanhidrinska reakcija, adicija cijano skupine na ,-nezasićene karbonilne spojeve, nukleofilna supstitucija halogenalkana cijanidom, Sandmeyerova reakcija, dehidratiranje amida i oksima, priprava nitrila iz zasićenih i nezasićenih ugljikovodika. Sljedeće poglavlje se odnosi na reaktivnost nitrila, obrađeni su mehanizmi reakcije hidrolize katalizirane kiselinom i bazom, redukcija nitrila katalitičkim hidrogeniranjem i kompleksnim metalnim hidridima, Grignardova reakcija te alkiliranje i aciliranje nitrila. U zadnjem poglavlju je opisana primjena nitrila u farmaciji i proizvodnji industrijski važnih materijala, te njihova zastupljenost u prirodnim spojevima.