Application of mathematical models in milk coagulation process during lactic acid fermentation. Part I. Relation betwen enzymmatic and acidic milk coagulation

Acidic and enzymatic coagulation of milk are complex processes which proceed in several phases and are dependent upon many different parameters. The formation of coagulum during lactic-acid fermentation is in fact acidic coagulation of milk. It occurs because of an increase in concentration of lactic acid, which causes a decrease in pH. Enzymatic coagulation of milk has been analytically described by means of mathematical models by many authors. Although enzymatic and acidic coagulation of milk do not proceed according to identical physical and chemical rules, it is possible to compare them kinetically. The aim of this paper was to combine the kinetics of enzymatic and acidic coagulation of milk and to mathematically present the changes that develop during lactic-acid fermentation of milk. The models presented in this paper enable a more complex mathematical analysis of the coagulation of the protein content of milk during lactic-acid fermentation. Application of the models enables the analysis and comparison of the kinetics of coagulation in different types of milk and various types of fermented dairy products manufactured with lactic acid bacteria. Mathematical combination of coagulation kinetics of the protein complex in milk with reological characteristics of the obtained fermented dairy products enables easier defining of parameters for lactic acid fermentation

Investigation of interactions of biologically active quinone avarone and its derivates with lysozyme, linear and circular deoxyribonucleic acid

Cilj našeg rada bio je ispitivanje biološke aktivnosti metilamino- i metoksiderivata avarona i razjašnjavanje mehanizma njihovog biološkog dejstva. Za sintezu su izabrani derivati za koje se očekivalo da će imati negativniji polutalasni potencijal od avarona i samim tim pokazivati povećanu aktivnost. Sintetisani su 4'-(metilamino)-avaron, 3'-(metilamino)-avaron i 3'-metoksi-avaron. Antibakterijska aktivnost dobijenih derivata je ispitivana prema gram-pozitivnim bakterijama: Bacillus subtilis, Clostridium sporogenes, Streptosporangium longisporum, Micrococcus flavus, Sarcina lutea i Staphylococcus aureus, prema gramnegativnim bakterijama: Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella enteritidis, Escherichia coli i prema kulturama gljivica: Aspergillus niger, Candida albicans i Saccharomyces cerevisiae disk-difuzionom metodom. Takođe, ispitivana je i toksičnost derivata na račiće Artemia salina. Potencijalna antioksidativna aktivnost avarona i dobijenih derivata ispitivana je testom sa DPPH. Antitumorska aktivnost ispitivana je za sve derivate na osam vrsta ćelija raka (ćelijske linije raka grlića materice, melanoma i leukemije, rak dojke pozitivan na estrogeni receptor, rak dojke negativan na estrogeni receptor, rak pluća, leukemija T-ćelija i promijelocitna leukemija) pri čemu je ispitivana i njihova citotoksičnost na limfocite. Svim hinonskim derivatima hemijski je modifikovan model-enzim lizozim. Dobijenim modifikatima lizozima je nakon modifikacije određena enzimska aktivnost. Sama modifikacija je praćena UV/Vis spektrofotometrijom, SDS elektroforezom i masenom spektrometrijom. Mesto vezivanja hinonskih derivata za molekul lizozima određeno je tehnikom MALDI TOF posle tripsinske digestije modifikata. S obzirom na uočeno vezivanje avaronskih derivata za ε-amino grupu lizina (Lys-97) u lizozimu, sintetisano je jedinjenje 4'-((5-tert-butoksikarbonil)amino)-5-karboksipentil)amino)- avarona, koje je poslužilo kao model jedinjenje za dalja ispitivanja biološke aktivnosti lizozim-hinonskog adukta...aim of our work has been investigation of biological activity of methylamino- and metoxy- derivatives of avarone, their bioconjugates of lysozyme and study of the mechanism of their biological action. For synthesis were chosen derivatives for which it was expected to have more negative half-wave potential than avarone and therefore a higher activity. The selected compounds are 3’-methylamino, 4’-methylamino- and 3’-methoxyavarone. Antimicrobial activity of the synthesized derivatives was investigated towards Gram positive bacteria: Bacilus subtilis, Clostridium sporogenes, Sreptosporangium longisporum., Micrococcus flavus, Sarcina lutea and Staphylococcus aureus, Gram negative bacteria: Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella enteritidis and Escherichia coli and fungi cultures: Aspergilus niger, Candida albicans and Sacharomyces cerevisiae, all by disc diffusion method. Toxicity against Artemia salina nauplii was surveyed as well. Antioxidant activity of avarone and its derivatives was assessed by DPPH assay. Antitumor activity was determined for all derivatives towards eight lines of tumor cells (myelogenous leukemia (K562), cervix carcinoma (HeLa), human malignant melanoma cells (Fem-X), Jurkat T cell leukemia, estrogen receptor negative breast carcinoma (MDA-MB-231), estrogen receptor positive breast carcinoma (MCF7), human fetal lung fibroblast (MRC-5) and human promyelocytic leukemia (HL-60)). For all derivatives toxicity towards lymphocytes was determined. Model enzyme lysozyme was modified with the synthesized quinones and for all the obtained bioconjugates MIC value towards Gram positive and Gram negative bacteria were determined. Modification reaction was monitored by UV/VIS spectrophotometry, SDS electrophoresis and mass spectrometry. Binding position of quinone derivatives on lysozyme was determined by MALDI TOF spectrometry after trypsin digestion. Since the avarone derivatives were found to bind to lysine (Lys-97) in lysozyme, 4’-((5-((tert-butoxycarbonyl)amino)-5-carboxypentyl)-amino)avarone has been synthesized as a model compound for further investigation of the biological activity of lysozyme―quinone aduct..

Supplementary data for the article: Dimitrijević, T.; Novaković, I.; Radanović, D.; Novaković, S. B.; Rodić, M. V.; Anđelković, K.; Šumar-Ristović, M. Synthesis, Spectral and Structural Characterization and Biological Activity of Cu(II) Complexes with 4-(Diethylamino)Salicylaldehyde and α-Diimines. Journal of Coordination Chemistry 2020, 73 (4), 702–716. https://doi.org/10.1080/00958972.2020.1740212

Supplementary material for: [https://doi.org/10.1080/00958972.2020.1740212]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/4025

Dobijanje i karakterizacija dva tipa imobilizovane amiloglukozidaze

Amyloglucosidase from A. niger was covalently immobilized onto poly(GMA-co-EGDMA) by the glutaraldehyde and periodate method. The immobilization of amyloglucosidase after periodate oxidation gave a preparate with the highest specific activity reported so far on similar polymers. The obtained immobilized preparates show the same pH optimum, but a higher temperature optimum compared with the soluble enzyme. The kinetic parameters for the hydrolysis of soluble starch by free and both immobilized enzymes were determined.Amiloglukozidaza iz A.niger je imobilizovana na poly(GMA-co-EGDMA) glutaraldehidnom i perjodatnom metodom. Imobilizacija amiloglukozidaze nakon perjodatne oksidacije daje preparat sa najvećom do sada objavljenom specifičnom aktivnosti na sličnim polimerima. Dobijeni imobilizovani preparat ima isti pH optimum ali povećani termooptimum u poređenju sa rastvornim enzimom. Određeni su i kinetički parametri za hidrolizu rastvornog skroba imobilizovanim kao i rastvornim enzimom

Hemijske modifikacije β-laktoglobulina hinonima

The avarone/avarol quinone/hydroquinone couple. as well as their derivatives show considerable antitumor activity. In this work, covalent modifications of beta-lactogglobulin. isolated from cow milk by avarone, its model compound 2-tert-butyl-1,4-benzoquinone. and several of their alkylthio derivatives were studied. The techniques applied for as-saying the modifications were: UV/VIS spectrophotometry, SDS PAGE and isoelectrofocusing. The results of the SDS PAGE suggest that polymerisation of the protein occurs. The shift of the pI of the protein upon modification toward lower values indicates that lysine amino groups are the principal site of die reaction of beta-lactoglobulin with the quinones.Hinonsko/hidrohinonski par avaron/avarol i njihovi derivati pokazuju značajnu antitumorsku aktivnost. U ovom radu proučavane su kovalentne modifikacije β-laktoglobulina, izolovanog iz kravljeg mleka, avaronom, njegovim model-jedinjenjem 2-tert-butil-1,4-benzohinonom i njihovim alkiltio-derivatima. Za ispitivanje modifikacija korišćene su UV/VIS spektrofotometrija, SDS PAGE i izoelektrofokusiranje. Rezultat SDS PAGE ukazuje da se protein polimerizuje. Pomeranje pI vrednosti proteina nakon modifikacije ka nižim vrednostima pokazuje da su amino grupe lizina glavna mesta reakcije β-laktoglobulina sa hinonima

Biocompatible nanostructure materials

Materials suitable for medical systems have always been the product of interdisciplinary collaboration between material and biological science. As well as different area of physics and chemistry. For medical application materials must not damage blood cells or bones and must be resistant. Some implant materials for chemical bonds can be stabilized by implantation of different elements or deposition of very thin films. In this work we presented some results for replacement of damaged human tissues.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Regioselektivnost konjugovane adicijena monoalkil-1,4-benzohinone

The regioselectivity of the reaction of conjugate addition of thiols, amines, methanol and hydrogen chloride with the monoalkyl-1,4-benzoquinones avarone and 2-tert-butyl-1,4-benzoquinone was investigated. It was shown that the regioselectivity of the reaction is influenced by the electrophilicity of position 5 in unprotonated 2-alkylquinones, the increased electrophilicity of position 6 in acidic medium, and by the acidity of the intermediate hydroquinones.Proučavana je regioselektivnost konjugovane adicije tiola, amina, metanola i hlorovodonika na monoalkil-1,4-benzohinone avaron i 2-tert-butil-1,4-benzohinon. Pokazano je da na regioselektivnost reakcije utiču elektrofilnost položaja 5 neprotonovanih 2-alkil-hinona i povećana elektrofilnost položaja 6 u kiseloj sredini, kao i kiselost intermedijernih hidrohinona

Supplementary material for the article: Vilipić, J. P.; Novaković, I. T.; Zlatović, M. V.; Vujčić, M. T.; Tufegdžić, S. J.; Sladić, D. M. Interactions of Cytotoxic Amino Acid Derivatives of Tert-Butylquinone with DNA and Lysozyme. Journal of the Serbian Chemical Society 2016, 81 (12), 1345–1358. https://doi.org/10.2298/JSC160725101V

Supplementary material for: [https://doi.org/10.2298/JSC160725101V]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2389

Supplementary data for article: Krstić, N. M.; Pavlović, V. D.; Novaković, I. T.; Matić, I. Z.; Sladić, D. Synthesis, Characterization and Biological Evaluation of Some Novel P-Heterocyclic Androst-4-Ene Derivatives. Molecular Diversity 2013, 17 (3), 547–561. https://doi.org/10.1007/s11030-013-9455-9

Supplementary material for: [https://doi.org/10.1007/s11030-013-9455-9]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1376

Najčešći uzroci studentskog otpora reformi visokog obrazovanja u Srbiji i regionu

U radu se analiziraju i objašnjavaju najvažniji uzroci studentskih štrajkova i javnih protesta protiv reforme visokog obrazovanja u Srbiji i regionu. Sociološka i ekonomska analiza omogućava autorkama da istaknu najvažnije društvene, ekonomske i političke karakteristike sredine u kojoj se dešavao studentski otpor, ali i da ovu istražuju u kontekstu evropskih integracija. Polazna teza glasi: studentski štrajkovi i protesti su u najvećoj meri sistemski determinisani, pre svega, prirodom društvenog sistema, karakteristikama vladajuće klase, lokalnim prilikama i mestom zemlje u evropskoj i svetskoj podeli rada u sferi obrazovanja. Studentski štrajkovi u Srbiji i regionu se značajno razlikuju u odnosu na one u svetu po dinamici, oblicima ispoljavanja i efikasnosti. Komparativni metod istraživanja se nametnuo kao nezaobilazan. Pored sociološke, ekonomske, politikološke naučne i iskustvene građe koriste se i drugi izvori podataka. U prvom delu navode se osnovni elementi reforme visokog obrazovanja u kontekstu evropskih idrugih integracija. Drugi deo je centralni deo istraživanja. To su najvažniji povodi i uzroci studentskih štrajkova i javnih protesta protiv reforme visokog obrazovanja, odnos političkih elita prema tome i stepen efikasnosti studentskog protesta. Treći deo istraživanja posvećen je poređenju sa onima u svetu (SAD, Kanada, Zapadna Evropa)