591 research outputs found
Sort by
Michael condensations of acetophenone and diethyl maleate
No full textCilj ovoga rada bio je sintetizirati produkte Michael-ovom kondenzacijom acetofenona i dietil-maleata klasičnom sintezom i uz prisutnost mikrovalnog zračenja. Michael-ovom kondenzacijom acetofenona i dietil-maleata u prisutnosti natrijeva etilata kao katalizatora dobivena su dva produkta. Istom reakcijom uz uporabu mikrovalnoga zračenja sintetizirani su identični produkti u znatno kraćem reakcijskom vremenu. Strukture dobivenih keto- i enolnih tautomera potvrđene su spektroskopskim metodama, kristalografijom i elementarnom analizom.Aim of this work was to investigate the effect of microwave irradiation on Michael condensation of acetophenone and diethyl maleate without and in the presence of microwave irradiation. Without microwave irradiation two products were obtained. Identical products were synthesized by microwave irradiation in a much shorter reaction time. The structures of keto- enol tautomers were confirmed by spectroscopic methods, crystallography, and elemental analysis
Oksidacije 1-benzotiofena (tianaftena)
No full textAromatski heterociklički spoj 1-benzotiofen, oksidacijom se prevodi iz sulfida u odgovarajući sulfon, 1 -benzotiofen-1,1-dioksid. U ovom radu 1 -benzotiofen je oksidiran u 1-benzotiofen-1,1-dioksid korištenjem vodene otopine vodikova peroksida i ledene octene kiseline kao otapala, uz refluksiranje i to u vrlo dobrom iskorištenju od 71 %. Oksidacija 1- benzotiofena je provedena i uz oksidirajući reagens H2O2-P2O5 i acetonitril kao otapalo, sa ili bez refluksiranja. Ovisno o metodi, iskorištenja su bila 3-48%. Korištenje H2O2-P2O5 reagensa je ekološki prihvatljivo i pokazalo se kao dosta dobro oksidacijsko sredstvo, koje se može primjeniti i za druge heterocikličke spojeve koji sadrže sumpor, a u slučaju 1 - benzotiofena osobito onda kada sadrži elektron-akceptorske skupine (EWG).The aromatic heterocyclic compound 1-benzothiophene can be oxidized from its sulfide functional group into a sulfone, 1-benzothiophene-1,1-dioxide. In this work 1- benzothiophene is oxidized into 1 -benzothiophene-1,1-dioxide by heating an aqueous solution of hydrogen peroxide and glacial acetic acid as a solvent at reflux, with a very good yield of 71 %. Oxidation of 1-benzothiophene was carried out with H2O2-P2O5 reagent and acetonitrile as solvent, with and without reflux. Depending on the method, yields were ranging from 3-48%. The use of H2O2-P2O5 reagent is environmentally acceptable and it has been demonstrated to be a good oxidation agent which can be applied for other heterocyclic compound that contain sulfur, especially for 1-benzothiophenes that contain electron-withdrawing groups (EWG)
Methods for determining particle size
No full textMetode određivanja veličine čestica sastavni su dio klasifikacije tvari i pomažu pri određivanju svojstava tvari i u konačnici njihove namjene. Budući da je tehnologija u zadnjih par desetljeća poprilično napredovala danas postoje različite metode određivanja veličine čestica. Neke od njih su sedimentacija, lasersko raspršenje, akustične metode, dinamičko raspršenje svjetla i električno očitavanje. Svaka metoda ima određene prednosti i mane u svojoj primjeni pa je prema tome i tekao put njihova daljnjeg razvijanja. Danas najpopularnija metoda za određivanje veličine čestica je metoda laserskog raspršenja. Odlikuju ju široka primjenjivost, jednostavnost izvedbe i brzina te mogućnost analize širokog spektra veličine čestica i disperzijskih sredstava. S druge strane, određivanje veličine čestica akustičnom spektroskopijom zanimljivo je zbog svojstva odvajanja apsorpcije od raspršenja, što je drugim metodama veoma teško postići. Pomoću ove metode moguće je odrediti veličinu čestica u koloidima i kašastim smjesama. Metoda se sastoji od širenja ultrazvučnih valova u određenom rasponu frekvencija kroz sustav čestica i preciznog mjerenja atenuacije na svakoj frekvenciji. Takav atenuacijski spektar može se pretvoriti u distribuciju veličine čestica i mjeru koncentracije dispergirane faze.Methods for determining particle size are a constituent part of substance classification and are very helpful in determination of substance properties and finaly their purpose. Since technology advanced in the last few decades there are various methods for determining particle size. Some of them are sedimentation, laser diffraction, acoustic methods, light scattering and electrical sensing. Each method has certain advantages and disadvantages in its application so their development went according to it. The most popular method for determining particle size today is laser diffraction. It is characterized by wide application, simple performance, speed and also the possibility to analize wide range of particle sizes and disperzions. On the other hand, determining particle size with acoustic spectroscopy is interesting because it separates absorption from scattering which is very hard to accomplish with other methods. With this method it is possible to determine particle size in colloids and slurries. The technique consists of propagating ultrasonic waves of a range of frequencies through the particulate system and accurately measuring the attenuation at each frequency. This attenuation spectrum can be converted to a particle size distribution and a measure of the concentration of the dispersed phase
Antioksidacijska aktivnost polifenolnih spojeva u sokovima
No full textFlavonoidi u posljednje vrijeme privlače puno pozornosti zbog svoje antioksidacijske i antiradikalske aktivnosti. Zbog toga su zanimljivi u prehrambenoj i farmaceutskoj industriji. Zadatak ovog rada je opisati i objasniti polifenolne spojeve i njihovu antioksidacijsku aktivnost u sokovima. Djelotvornost polifenolnih spojeva, kao hvatača slobodnih radikala, uvjetovan je rasporedom slobodnih hidroksilnih skupina na flavonoidnoj jezgri. OdreĎen je sadržaj polifenolnih spojeva i njihova antioksidacijska aktivnost u voću, njihovim džemovima i svježim i uskladištenim voćnim sokovima. Dokazano je i sinergističko djelovanje vitamina C i polifenola.Flavonoids recently attracted much attention due to their antioxidant and antiradical activity. Because they are interesting in the food and pharmaceutical industries. The task of this paper is to describe and explain polyphenolic compounds and their antioxidant activity in the juices. Effectiveness of polyphenolic compounds, free radical scavengers, is determined by the schedule of free hydroxyl groups on flavonoids core. The contents of polyphenolic compounds and their antioxidant activity in fruits, their jams and fresh fruit juices and stored. It's proved a synergistic action of vitamin C and polyphenolic compound
Izolacija karotenoida
No full textU prirodi se javlja mnogo obojenih tvari čija se boja temelji na apsorpciji djela vidljivog spektra sustavom konjugiranih veza. Narančasti i crveni pigmenti u voću i povrću su ugljikovodici pod nazivom karotenoidi. Boju karotenoida ne čini jedan spoj, već smjesa spojeva. Zadatak ovog rada bila je izolacija i identifikacija karotenoida iz mrkve, rajčice, svježe i mljevene paprike. Za identifikaciju spojeva koji se nalaze u ovom povrću korištena je tankoslojna kromatografija dok je za pročišćavanje korištena kromatografija na stupcu. Kloroform, koji je nepolarno otapalo, korišten je u postupku izolacije. Kromatogram je razvijen u kloroformu, a za kolonsku kromatografiju je korištena smjesa otapala aceton : petroleter u volumnom omjeru 10:90. Kod dobivenih rezultata vidi se da mljevena i svježa paprika sadrže iste karotenoide. Vidljivo je da mrkva sadrži smjesu karotena, α-karoten, β-karoten i γ-karoten. Rajčica sadrži likopen i β-karoten i neke ksantofile, žuto obojene karotenoide.In nature occurs a lot of colored substences which color is based on absorption of visible spectrum by conjugated system. Orange and red pigments in fruits and vegetables are hydrocarbons called carotenoids. Carotenoids color does not make one compound, but a mixture of compounds. Carotenoid in carrot, tomato and fresh and ground pepper are isolated and identified. For identification of carotenoid in vegetables was used thin layer chromatography (TLC) and for purification column chromatography. Chloroform, which is a non polar solvent, were used in the proces of isolation. As mobile phase in TLC was used chloroform and for column chromatography was used a mixture of solvents of aceton:petroleum ether in volume ratio 10:90. As the result is shown that fresh and ground pepper contain the same carotenoid. Mixture of carotens was found in carrot, α-caroten, β- caroten and γ-caroten. Tomato contains lycopene and β-caroten and some xantophyls, yelow colored carotenids
Synthesis of Sulfimide and Sulfoximide Derivatives of Benzo[b]thiophene
No full textPrema dostupnoj literaturi, do danas je poznat samo jedan sulfiliminski derivat benzo[b]tiofena te sulfiliminski i sulfoksiminski derivati monocikličkog tiofena. VoĎeni tom spoznajom u ovom radu su pripremljeni poznati sulfiliminski te potpuno novi sulfoksiminski derivat benzo[b]tiofena. Poznatom sintezom sulfilimina N[1λ4benzo[b]tiofeniliden]-4-metilbenzensulfonamida (15) priredio se spoj čijom oksidacijom smo ţeljeli dobiti njegov sulfoksimin. Nakon nekoliko pokušanih oksidacija kao i pripreme drugih analoga prethodno navedenog sulfilimina, uspješno je pripremljen sulfoksimin 4- metil-N-[1-okso-1H-1λ6benzo[b]tiofen-1-iliden]benzensulfonamid oksidacijom pomoću H2O2-P2O5 reagensa. Sulfoksimin 17 je sulfoksiminski derivat benzo[b]tiofena. Usporedbom IR spektra, 1H i 13C NMR spektra sulfilimina 15 i sulfoksimina 17 utvrĎeno je da se radi o novom spoju.According to the available literature, up to present date, only one sulfilimine derivative of benzo[b]thiophene is reported and several sulfilimine and sulfoximine derivatives of monocyclic thiophene. Guided by this fact, we have prepared the reported sulfilimine and new sulfoximine derivative of benzo[b]thiophene that was previously unknown. The known synthesis of sulfilimine N- [1λ4-benzo[b]thiophenylidene]-4-methylbenzenesulfonamide (15) was followed in order to oxidise it and to obtain its sulfoximine. After few attempted oxidations, as well as preparations of other analogues of the aforementioned sulfilimine, we have successfully prepared sulfoximine 4-methyl-N- [1-oxo-1H-1λ6benzo[b]thiophen-1-ylidene]benzenesulfonamide by oxidation with H2O2-P2O5 reagent. Sulfoximine 17 is in fact sulfoximine derivative of benzo[b]thiophene. The comparison between the IR spectrum, 1H and 13C NMR spectra of sulfilimine 15 and sulfoximine 17 confirmed this is a new compound with the proposed structure
Determination of diastase in honey using direct potentiometry
No full textDijastaza je i jedan od enzima u medu. Dijastazu u medu čine α-amilaza, koja razlaže škrob na maltozu i izomaltozu te β-amilaza koja ga razlaže na β -maltozu. Amilaze su probavni enzimi koji kataliziraju hidrolizu škroba dajući produkte u obliku dekstrina, oligosaharida, maltoze ili D-glukoze, ovisno o tipu amilaze. Škrob stvara plavo obojeni kompleks s trijodididnim ionom smanjujući tako početnu koncentraciju trijodida u otopini. Zbog navedenog svojstva, ta reakcija se koristi pri spektrofotometrijskom određivanju koncentracije škroba u otopini. S obzirom da ga dijastaza razgrađuje, koncentracija škroba je obrnuto proporcionalna koncentraciji dijastaze u medu, te se može pratiti promjena koncentracije škroba ovisno o aktivnosti dijastaze. Promjenom koncentracije trijodidnog iona u otopini kompleksa škrob-trijodid i dijastaze dolazi do promjene vrijednosti omjera redoks-para trijodid/jodid, a to prema Nernstovoj jednadžbi uzrokuje promjenu elektrodnog potencijala redoks senzora, što je direktno povezano s koncentracijom dijastaze. Primjenom direktne potenciometrije prati se promjena redoks potencijala otopine i vidljiva je različita aktivnost dijastaze u različitim vrstama meda.Diastase is one of the most important ingredients of honey. Diastase in honey consist of α- amylase, which breaks down starch to maltose and isomaltose and β-amylase, which breaks it down to β-maltose. Amylases are digestive enzymes that catalyze the hydrolysis of starch, giving the products in the form of dextrin, oligosaccharides, maltose or Dglucose, depending on the type of amylase. Starch forms blue colored complex with triiodide ion reducing the initial concentration of triiodide in solution. This reaction is used for spectrophotometric determination of starch concentration in solution. As diastase breaks it down, starch concentration is inversely proportional to the concentration of diastase in honey. This could be used to monitor changes in concentration of starch depending of diastase concentration. Changing the triiodide ion concentration in starch-triiodide complex the ratio of redox couples triiodide / iodide changes. According to the Nernst eqation, this causes a change in electrode potential of redox sensor, which is directly related to the concentration of diastase. Redox potential changes in investigetad solution can be measured applying direct potentiometry resulting in different diastase activity of different honey types
Potenciometric study of starch-triiodide system
No full textŠkrob je ugljikohidrat koji se sastoji od dva polimera: amiloze i amilopektina. Amiloza stvara stabilne komplekse sa trijodidnim ionom, dok amilopektin stvara vrlo slabe komplekse. Prilikom nastanka škrob-trijodid kompleksa otopina se oboji u tamno plavo, tako da može služiti kao indikator. Udio amiloze i/li amilopektina varira ovisno o vrsti škroba. Pratio se odziv platinske redoks elektrode na različite vrste i sorte škrobova pri različitim masama dodanog škroba. Uporabom direktne potenciometrije mjeri se ovisnost elektrodnog potencijala o količini dodane otopine škroba u otopinu kalijevog trijodida. Mjereni su uzorci škrobova različitog botaničkog podrijetla. Grafičkim prikazom rezultata utvrđeno je da postoji razlika u odgovoru platinske redoks elektrode s obzirom na vrstu korištenog škroba. Razlike se odnose na izgled grafa, odnosno na razlike u promjeni potencijala do stvaranja maksimalne koncentracije kompleksa škrob-trijodid te na nagib odgovora redoks elektrode s povećanjem koncentracije dodanog škroba.Starch is carbohydrate and a mixture of two polimers: amylose and amylopectin. Amylose creates strong complexes with triiodide, but amylopectin doesn't. Starch-triiodine complex causes dark blue coloration and it can be used as an indicator. Amount of amylose and/or amylopectin is different in different types of starch. We were watching response of a platinum redox electrode on diferrent species and varieties of starches using different masses of starch and concentration of triiodide. We were measuring, using direct potentiometry, how electrode potential depends of a amount of starch solution added to a solution of potassium triiodide. Samples of starch had different botanical origin. Graphical presentation of results showe that there is a difference in the response to a platinum redox electrode considering the type of starch. The differences related to the appearance of the graph, the difference in changing the potential to create the maximum concentration of the complex starch-triiodide and the slope response of the redox electrode with increasing concentrations of added starch
Potenciometrijska titracija kationskih tenzida i etoksiliranih neionskih tenzida
No full textZa određivanje kationskih i neionskih tenzida potenciometrijskom titracijom korišten je osjetljivi tenzidni senzor baziran na 1,3-didecil-2-metil-imidazolijevom kationu i tetrafenilboratnom (TPB) antagonist-ionu kao detektoru završne točke pri potenciometrijskoj titraciji. Natrijev tetrafenilborat upotrebljen je kao titrant. Potenciometrijskom metodom titrirano je nekoliko kationskih (CS) i etoksiliranih neionskih tenzida (EONS), analitičke i tehničke čistoće, pojedinačno i u smjesi. Senzor je pokazao zadovoljavajuće rezultate u rasponu pH 3-10, te zadovoljavajuću selektivnost za sve ispitivane kationske i neionske tenzide. Ionska jakost nije bitno utjecala na titraciju, osim pri koncetraciji 0,1 M NaCl, gdje je došlo do manjeg izobličenja druge točke infleksije koja odgovara titraciji neionskog tenzida. Različite kombinacije dvokomponentnih smjesa četiri kationska i tri etoksilirana neionska tenzida titrirane su potenciometrijski koristeći ranije navedeni senzor kao detektor završne točke. Količine ispitivanih tenzida varirale su između 2 i 6 µmolova za kationski tenzid te 2,50 i 7,50 µmolova za etoksilirani neionski tenzid. Veće pogreške javljale su se ako je odnos utrošaka titranta za svaku komponentu u smjesi premašilo vrijednost 3:1. Pogreške se mogu značajno smanjiti izvođenjem preliminarne titracije i naknadnim dodatkom poznate količine tenzida prisutnog u nižoj koncentraciji.A sensitive potentiometric surfactant sensor based on a highly lipophilic 1,3-didecyl-2-methyl-imidazolium cation and a tetraphenylborate antagonist ion has been used as the endpoint detector in ion-pair surfactant potentiometric titrations using sodium tetraphenylborate as titrant. Several analytical and technical grade cationic (CS) and ethoxylated nonionic surfactants (EONS), single and the mixtures of both were potentiometrically titrated. The sensor showed satisfactory analytical performances within a pH range of three to ten, and exhibited satisfactory selectivity for both, CS and EONS investigated. The ionic strength didn't influence the titration except at 0.1 M NaCl, where a slight distortion of the second inflexion related to the nonionic surfactant was evidenced. Any two-component combination of four CS and three EONS has been potentiometrically titrated using the sensor mentioned as the end-point detector. The quantities of the surfactants investigated varied between 2 and 6 µmols for CS and 2,50 and 7,50 µmols for EONS. The larger errors appeared if the ratio of titrant consumptions for each component in the mixture exceeds the value of 3:1 can be significantly reduced by performing a preliminary titration and a subsequent known addition of the surfactant present at lower concentration
The role of calpains in muscle tissue proteolysis
No full textoai:repozitorij.kemija.unios.hr:kemos_1Kalpainski enzimski sustav čine dvije sveprisutne proteaze, μ-kalpaina i m-kalpaina, te njihov inhibitor, kalpastatin. Kalpaini su heterodimeri koji se sastoje od dvije podjedinice: velike katalitičke veličine 80 kDa organizirane u četiri domene, te male regulatorne veličine 30 kDa organizirane u dvije domene. Na temelju dosadašnjih saznanja o katalitičkim svojstvima kalpaina, aktivnost kalpaina se regulira koncentracijom Ca2+, autproteolizom, kalpastatinom, staničnom lokalizacijom i specifičnim područjem aktivnog mjesta. Kalpaini sudjeluju u različitim staničnim procesima uključujući staničnu mobilnost, prijenos signala, stanični ciklus, apoptozu, patološke bolesti i postmortalnu proteolizu. Mehanizam posmortalne proteolize mesa je vrlo složen proces u kojem sudjeluje velik broj različitih enzima. Glavnu ulogu u miofibrilarnoj proteolizi imaju kalpaini. Miofibrilarna žilavost posljedica je mrtvačke ukočenosti, dok je miofibrilarno omekšavanje uzrokovano cijepanjem miofibrilarnih proteina kalpainima. Na temelju važnih dosadašnjih dokaza, razjašnjeni su mnogi faktori koji utječu mekoću mesa.The calpain system consist of calpains, a family of Ca2+ dependent cysteine proteases whose members are expressed ubiquitously or in a tissue-specific way. Calpains are heterodimeric proteins, composed of catalytic subunit of about 80 kDa organised in 4 domains and the small 30 kDa subunit organised in 2 domains. Based on the current knowledge of the catalytic properties of the calpains, it seems that calpain activity is regulated by Ca2+ concentration, calpastatin, intracellular location and subsite specificity of the calpains. Calpains participate in a variety of cellular processes including cell motility, signal transduction pathways, the cell cycle, apoptosis, long-term potentiation, pathological states in cells and postmortem proteolysis. The exact mechanisms involved in the postmortem meat tenderization process are complex and includes a large number of different enzymes. The main myofibrillar proteolysis can be attributed to calpains. The myofibrillar toughness is considered to be affected by the development of rigor-mortis and tenderization caused by calpains break-down of the contractile proteins. Based on the relevant evidence thus far obtained, factors affecting meat tenderness, although not fully understood, are in perspective to be clarified