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Varroa destructor is a parasitic mite responsible for the loss of honey bee (Apis mellifera) colonies. This study aimed to find a promising marker in honey for the bee colony infestation level using fluorescence spectroscopy and biochemical analyses. We examined whether the parameters of the honey samples’ fluorescence spectra and biochemical parameters, both related to proteins and phenolics, may be connected with the level of honey bee colonies’ infestation. The infestation level was highly positively correlated with the catalase activity in honey (r = 0.936). Additionally, the infestation level was positively correlated with the phenolic spectral component (r = 0.656), which was tentatively related to the phenolics in honey. No correlation was found between the diastase activity in honey and the colonies’ infestation level. The results indicate that the catalase activity in honey and the PFC1 spectral component may be reliable markers for the V. destructor infestation level of the colonies. The obtained data may be related to the honey yield obtained from the apiaries.

Varroa destructor is a parasitic mite responsible for the loss of honey bee (Apis mellifera) colonies. This study aimed to find a promising marker in honey for the bee colony infestation level using fluorescence spectroscopy and biochemical analyses. We examined whether the parameters of the honey samples’ fluorescence spectra and biochemical parameters, both related to proteins and phenolics, may be connected with the level of honey bee colonies’ infestation. The infestation level was highly positively correlated with the catalase activity in honey (r = 0.936). Additionally, the infestation level was positively correlated with the phenolic spectral component (r = 0.656), which was tentatively related to the phenolics in honey. No correlation was found between the diastase activity in honey and the colonies’ infestation level. The results indicate that the catalase activity in honey and the PFC1 spectral component may be reliable markers for the V. destructor infestation level of the colonies. The obtained data may be related to the honey yield obtained from the apiaries.

Previously, the cytotoxic actions of five Pd(II) complexes with bidentate N-heteroaromatic chelators (complexes 1–5) on a palette of several cancercell lines were investigated. However, the results of the cytotoxic activity didnot correlate with the hydrophobic character of the complexes. To gain furtherinsight into the structure–activity relationship, essential for the design of novelpotential drugs, other factors, such as non-specific interactions with cellularproteins, have to be taken into account. To explore the potential non-specificinfluence of the complexes on protein structures, ovalbumin (OVA) waschosen as a model system to mimic cellular non-specific crowding environments with high protein concentrations. A Fourier-transform infrared spectroscopy study implied that the binding of 3 and 4 led to only moderate alternations in the secondary structures of the protein, without the possibility to penetrate into hydrophobic core of the protein and disruption of protein native fold.Contrary, the effect of complex 5 on OVA secondary structures was concentration-dependent. While the lower concentration of complex 5 had no effecton OVA structure, a doubled concentration of complex 5 led to complete disruption of the content native-like secondary structures. The concentration-dependent effect of complex 5 on the changes in secondary structures and considerable increase in the exposure of OVA hydrophobic surfaces to water maybe related to a potential crosslinking that leads to OVA aggregation.

SDS-PAGE showing: Lane 1 – purified banana lectin – BanLec; Lane 2 – chimera of banana lectin and enhanced green fluorescent protein BanLec-eGFP; Lane 3 – MW – molecular weight markers; Table 1. Repeatability of flow cytometric detection of different quantities of BL-eGFP binding to C. albicans; Table 2. Repeatability of ELLSA detection of different quantities of BanLec-B binding to C. albicans; Table 3. Repeatability of flow cytometric detection of different quantities of RCA120-FITC binding to L. casei DG; Table 4. Repeatability of ELLSA detection of different quantities of RCA120-B binding to L. casei DG; Table 5. Reproducibility of BanLec-B binding to 21 different microorganisms. Experiments were done in three different laboratories, with preparing new plates each time; Fig. 1 Determining linearity of ELLSA method, by measuring binding between C.albicans and different quantity of BanLec-B; Fig. 2 Determining linearity of flow cytometry, by measuring binding between C.albicans and different quantity of BanLec-eGFP; Fig. 3 Determining linearity of ELLSA method, by measuring binding between L.casei DG and different quantity of RCA120; Fig. 4 Determining linearity of flow cytometry, by measuring binding between L.casei DG and different quantity of RCA120.

Previously, the cytotoxic actions of five Pd(II) complexes with bidentate N-heteroaromatic chelators (complexes 1–5) on a palette of several cancer cell lines were investigated. However, the results of the cytotoxic activity did not correlate with the hydrophobic character of the complexes. To gain further insight into the structure–activity relationship, essential for the design of novel potential drugs, other factors, such as non-specific interactions with cellular proteins, have to be taken into account. To explore the potential non-specific influence of the complexes on protein structures, ovalbumin (OVA) was chosen as a model system to mimic cellular non-specific crowding environments with high protein concentrations. A Fourier-transform infrared spectroscopy study implied that the binding of 3 and 4 led to only moderate alternations in the secondary structures of the protein, without the possibility to penetrate into hydrophobic core of the protein and disruption of protein native fold. Contrary, the effect of complex 5 on OVA secondary structures was concentration-dependent. While the lower concentration of complex 5 had no effect on OVA structure, a doubled concentration of complex 5 led to complete disruption of the content native-like secondary structures. The concentration-dependent effect of complex 5 on the changes in secondary structures and considerable increase in the exposure of OVA hydrophobic surfaces to water may be related to a potential crosslinking that leads to OVA aggregation.

Papain is a proteolytic enzyme of great commercial value. It is a cysteine protease highly expressed in Carica papaya fruit latex, but also present in papaya leaves. Purification procedures mostly deal with the latex and include a combination of precipitation and/or chromatographic techniques. Due to its solubility, structure and activity characteristics, the pH and salt content play significant roles in handling papain extracts. Here we report a simple, rapid and easily scalable procedure for papain purification from papaya leaves, which contain different contaminants as compared to papaya latex. Sodium chloride precipitation of contaminants at pH 5 followed by ammonium sulphate precipitation resulted in the removal of other leaf proteins and protein fragments from papain solution and about a 3-fold purification. The procedure also benefits from the suppression of autoproteolysis and preservation of the native structure, as confirmed by FTIR analysis, and the high recovery of activity of over 80%.

Oligomeric intermediates on the pathway of amyloid fibrillation are suspected as the main cytotoxins responsible for amyloid-related pathogenicity. As they appear to be a part of the lag phase of amyloid fibrillation when analyzed using standard methods such as Thioflavin T (ThT) fluorescence, a more sensitive method is needed for their detection. Here we apply Fourier transform infrared spectroscopy (FTIR) in attenuated total reflectance (ATR) mode for fast and cheap analysis of destabilized hen-egg-white lysozyme solution and detection of oligomer intermediates of amyloid fibrillation. Standard methods of protein aggregation analysis— Thioflavin T (ThT) fluorescence, atomic force microscopy (AFM), and 8-anilinonaphthalene-1-sulphonic acid (ANS) fluorescence were applied and compared to FTIR spectroscopy data. Results show the great potential of FTIR for both, qualitative and quantitative monitoring of oligomer formation based on the secondary structure changes. While oligomer intermediates do not induce significant changes in ThT fluorescence, their secondary structure changes were very prominent. Normalization of specific Amide I region peak intensities by using Amide II peak intensity as an internal standard provides an opportunity to use FTIR spectroscopy for both qualitative and quantitative analysis of biological samples and detection of potentially toxic oligomers, as well as for screening of efficiency of fibrillation procedures.

Measurement of antithyroglobulin antibodies (TgAb) is an inevitable laboratory tool in the management of thyroid gland diseases. Currently available immunoassays still have limitations underlying the necessity of the introduction of fast, sensitive, and label-free technologies. Our aim was to develop a method for TgAb measurement in human serum based on the quartz crystal microbalance (QCM) technology. We immobilized thyroglobulin on the surface of Attana LNB Carboxyl sensor chip®, prepared standard curve covering the range of 1–50000 kIU/L, and established optimal measurement conditions. The validation included determination of the detection limit (LOD), functional sensitivity, linearity, precision, as well as the comparison with the results of the radioimmunoassay (RIA). The LOD and functional sensitivity were 4.2 kIU/L and 4.7 kIU/L, respectively. The method was linear in the range of 20–10000 kIU/L. The regression equation for comparison with RIA was CQCM = 1.0056 • CRIA – 24.2778, whereby no significant proportional or systematic difference was present. There was a good agreement with RIA in the classification of patients according to the clinical significance of the results. The developed method has advantages over currently available assays in terms of better LOQ, a higher upper limit of linearity, and precision. The characteristics of the developed method unambiguously show that the application of the QCM biosensors offers a highly reliable novel approach for the measurement of TgAb in human serum.

Removal of phenolic compounds from water is of major interest over the years, since they are one of the most common pollutants in aqueous systems. Horseradish peroxidase (HRP) is the most investigated biocatalyst for this purpose. Inactivation of the enzyme is a major issue which can be successfully overcome by the enzyme immobilization on different polymers. In this study, tyramine-alginate micro-beads were used as carriers for the immobilization of horseradish peroxidase. The effect of the oxidation degree of tyramine-alginates on a specific activity of the enzyme was tested. An increase in the concentration of oxidized alginate from 2.5 to 20% resulted in a gradual increase in the specific activity from 0.05 to 0.67 U/mL. HRP immobilized within these micro-beads was tested for the phenol removal in a batch reactor. Reaction conditions were optimized to achieve a high removal efficiency and substantial reusability of the system. In this study, for the first time, an internal generation of hydrogen peroxide from glucose and glucose oxidase was employed in the phenol removal process with HRP immobilized on tyramine-alginate. Within 6 h of repeated use 96% of phenol was removed when the system for internal delivery of H2O2, composed of 0.187 U/mL of glucose oxidase and 4 mmol/L of glucose was employed. A common straightforward addition of hydrogen peroxide provided the removal efficiency of only 42%, under the same reaction conditions. The highest efficiency of the phenol removal (96%) was obtained with HRP immobilized within 20 mol% oxidized tyramine-alginate micro-beads. Fifteen mol% oxidized tyramine-alginate showed lower removal efficiency in the first cycle of use (73%) but more promising reusability, since the immobilized enzyme retained 61% of its initial activity even after four consecutive cycles of use.

Pectins are a group of heterologous polysaccharides capable of forming hydrogels and applicable in many industrial processes. A new type of modified pectin was synthesized by periodate oxidation and reductive amination with dopamine and sodium cyanoborohydride. The success of modification was confirmed by UV–Vis,FTIR, and 1H NMR spectroscopy. The obtained dopamine-pectin could form hydrogels by ionic crosslinking of carboxyl groups with calcium or by crosslinking phenol groups with laccase. For enzymatic crosslinking with laccase from Streptomyces cyaneus expressed in E. coli, isolation and purification of the enzyme was done. Using emulsion-based enzymatic crosslinking polymerization, dopamine-pectin microbeads with immobilized laccase were made. The immobilized laccase showed improved thermal and pH stability in comparison to the free enzyme. The immobilized biocatalyst effectively decolorized various dyes: Amido Black 10B, Reactive Black 5, and Evans Blue. After ten cycles of repeated use, the microbead immobilized laccase could still decolorize 60% and 36% of Amido Black 10B and Reactive Black 5, respectively.

Nemogućnost kontrole pojave i širenja rezistencije na antibiotike usmerila je istraživanja u poslednje dve dekade ka iznalaženju novih terapeutskih opcija, sa ciljem tretmana infekcija izazvanih patogenim bakterijama rezistentnim na veći broj kliniĉki znaĉajnih antibiotika. Uzevši u obzir ĉinjenicu da je antibiotska rezistencija kompleksan, multifaktorijalni fenomen, rešenje ovog problema ukljuĉuje niz pristupa usmerenih na kontrolu faktora koji olakšavaju nastanak i širenje rezistencije. Jedan od tih pristupa sastoji se u razvoju novih terapeutika koji bi delovali mehanizmima razliĉitim od trenutno dostupnih antibiotika. U tom pogledu, antivirulentna terapija zamišljena je kao obećavajuća alternativa sa ciljem kontrole virulencije specifiĉne za odreĊene patogene, bez vršenja snažnog selektivnog pritiska na bakterijske ćelije. Imajući u vidu da je Pseudomonas aeruginosa jedan od vodećih uzroĉnika unutarbolniĉkih infekcija širom sveta, leĉenje infekcija izazvanih ovim patogenom predstavlja veliki terapeutski izazov. P. aeruginosa svoj patogeni potencijal ostvaruje zahvaljujući mnogobrojnim uroĊenim, steĉenim i adaptivnim mehanizmima rezistencije. Pored toga, posedovanje sistema meĊućelijske komunikacije (eng. quorum sensing, QS) ovom patogenu omogućava fleksibilnost u regulaciji ekspresije gena ukljuĉenih u virulenciju, formiranje biofilma, produkciju sekundarnih metabolita i faktora koji imaju ulogu u zaštiti od imunskog sistema domaćina. Stoga bi primena antivirulentne terapije zasnovane na utišavanju meĊućelijske komunikacije bakterija mogla poslužiti kao obećavajuće oruĊe u kontroli infekcija izazvanih predstavnicima P. aeruginosa za koje ne postoji adekvatna terapija trenutno dostupnim antibioticima. U skladu sa time, predmet prouĉavanja ove teze bila je potraga za novim utišivaĉima meĊućelijske komunikacije bakterija (eng. quorum quenching, QQ) produkovanih od strane kliniĉkih izolata koji tokom infekcija dele istu ekološku nišu sa P. aeruginosa. Analizirana je, finding novel therapeutic options to combat multidrug-resistant pathogenic bacteria during the last two decades. Given the fact that antimicrobial resistance is a complex, multifactorial phenomenon, the solution to this problem comprises a range of approaches focused on monitoring the factors that facilitate the emergence and spread of resistance. One of proposed strategies consists of developing novel therapeutics that operate under different principles to the currently available antibiotics. In this respect, antivirulence therapy has been conceived as a promising alternative to control virulence in a pathogen-specific manner, without exerting strong selective pressure on the bacterial cells. Having in mind that Pseudomonas aeruginosa has been considered as a leading cause of nosocomial infections worldwide, the treatment of infections caused by this pathogen represents a major therapeutic challenge. The pathogenic potential of P. aeruginosa has been accomplished due to a numerous innate, acquired, and adaptive resistance mechanisms. In addition, the presence of cell-to-cell communication system (quorum sensing, QS) allows this pathogen the flexibility in the regulation of virulence gene expression responsible for biofilm development, production of secondary metabolites, and immuneevasive factors. Therefore, the use of antivirulence therapy based on the silencing of bacterial communication could serve as a promising tool in the control of infections caused by P. aeruginosa for which there is no adequate therapy with currently available antibiotics. Accordingly, the subject of this thesis was discovery and characterization of novel quenchers of bacterial cell-to-cell communication produced by clinical isolates that share the same ecological niche with P. aeruginosa during infections. A collection of Gram-negative clinical isolates from the Laboratory for Molecular Microbiology Institute of Molecular Genetics and Genetic Engineering University of Belgrade was analyze

Latex of common fig (Ficus carica) is a rich protein source with a high level of proteolytic activity contributing to its defensive role. The divergent group of cysteine proteases known as ficin (EC 3.4.22.3) represents the majority of latex protein content and shows activity towards fig parasites. Both classical and novel biochemical techniques suggest the intricate pattern of ficin expression and activity profiles. Even though structurally related, different ficin isoforms show some differences in pI values enabling their separation using ion-exchangers. A single alkaline isoform was purified and identified based on the available transcriptomic data as Ficin 1c. This isoform shows both general proteolytic and gelatinolytic activity suggesting a biological role in the degradation of a broad range of natural substrates. The insight into the Ficin 1c structure also provided some functional clues. The secondary structure content and the overall fold are similar to related proteases of the same and other plant sources resulting in similar unfolding routes. Stability assessment of Ficin 1c in comparison to ficin isoform mixture showed that isoform diversity might lead to increased protease stability.

Numerous applications of proteolytic enzymes include dissociation of fermented meat products for the enumeration of `foodborne pathogenic bacteria. The use of trypsin for this cause is abandoned due to the high concentration of the enzyme affecting released bacteria. Papain, as a suggested replacement, and fig latex preparation with high extent of papain-like enzymes have the potential to be applied for bacteria enumeration. Both enzymatic preparations, originating from papaya and fig, showed a broader range of substrate specificities including gelatinolytic activity, especially prominent in the case of ficin and attributed to both, cysteine protease ficin and serine protease by the analysis of 2D zymography with specific inhibitors. The activity towards native collagen, mild in the case of papain, and extensive in the case of fig latex was proved by structural analysis of digested collagen by infrared spectroscopy. Further exploration of their potential for dissociation of fermented meat products showed that both papain and fig latex enzymes are stable in the presence of detergents Tween 20 and Triton X-100 and effective in the enumeration of Listeria monocytogenes. Gelatenolytic activity, and at least partial collagenolytic activity and stability in procedure conditions make papaya and fig latex proteases potent for this application in significantly lower concentrations than previously used enzymes. As a mixture of proteolytic enzymes with divergent characteristics, fig latex preparation shows higher efficiency in Listeria monocytogenes release than papain, conserved even in the presence of stronger non-ionic detergent Triton X-100.

Сумпор-сумпор интеракције су препознате у многим молекулским системима, где су одговорне за молекулску структуру и функцију многих познатих неорганских и органских материјала као и протеина. У овој докторској дисертацији проучаване су геометрије и енергије сумпор-сумпор интеракција анализом података из кристалних структура и применом квантнохемијских прорачуна високог нивоа теорије..., Sulfur-sulfur interactions have been recognized in various molecular systems, where they are responsible for the molecular structure and function of many well known inorganic and organic moleculs and proteins. This doctoral study investigates the geometries and energies of sulfur-sulfur interactions by analyzing data obtained from crystal structures and by high-level quantum chemical calculations...

Celobioza – dehidrogenaza poreklom iz Phanerochaete chrysosporium, gljive bele truleži, pripada ekstracelularnim oksidoredukcionim enzimima i katalizuje oksidaciju β – 1,4 – glikozidno vezanih oligosaharida poput celobioze i laktoze. Oksidacijom laktoze dolazi do formiranja laktobionske kiseline koja pronalazi veliku primenu u farmaceutskoj i kozmetičkoj industriji gde se koristi prilikom distribucije lekova i za hidrataciju kože kao sastavni deo različitih krema, gde zajedno sa hijaluronskom kiselinu ima ulogu u smanjenju bora.Celobioza – dehidrogenaza prilikom oksidacije laktoze ili celobioze, kao prirodnih supstrata, katalizuje redukciju jednog dvoelektronskog ili dva jednoelektronska akceptora elektrona. Jedan od najkorišćenijih dvoelektronskih akceptora elektrona je upravo dihlor fenol indofenol (DCIP), dok jednoelektronski akceptori elektrona mogu biti citohrom c, ABTS, ali i Fe3+ i Mn3+ joni. Redukcijom Fe3+ jona u prisustvu molekulskog kiseonika dolazi do formiranja vodonik peroksida i posredstvom Fentonove reakcije do generisanja hidroksil radikala.Polazeći od ove činjenice, iskoristili smo upravo Fentonovu reakciju za razvoj fluorescentnog eseja za visoko efikasnu pretragu biblioteka gena celobioza – dehidrogenaze, baziranog na detekciji proizvedenih hidroksil radikala fluorogenom probom aminofenil – fluoresceinom (APF).Primena celobioza – dehidrogenaze u konstruisanju biosenzora i biogorivnih ćelija leži upravo u njenoj sposobnosti da katalizuje oksidaciju laktoze, celobioze i β – 1,4 – vezanih oligosaharida do odgovarajućih laktona koji potom spontano hidrolizuju do aldonskih kiselina. Enzimi koji nalaze primenu u konstruisanju biosenzora i biogorivnih ćelija, moraju da zadovoljavaju nekoliko kriterijuma,odnosno moraju da imaju veliku osetljivost i supstratnu specifičnost, ali i da pokazuju povećanu stabilnost..., Cellobiose dehydrogenase from Phanerochaete chrysosporium, a white rot fungus, belongs to the extracellular oxidoreductive group of enzymes and catalyzes the oxidation of the β – 1,4 – glycoside bond of oligosaccharides such as cellobiose and lactose. During oxidation of lactose, formation of lactobionic acid occurs which has many applications in pharmaceutical and cosmetic industry. Such applications include the distribution of medicine, a component responsible for skin hydration and when combined with hyaluronic acid as an agent against wrinkles.During oxidation of lactose or cellobiose by cellobiose dehydrogenase, reduction catalysis occurs of one two electron or two one electron acceptors. One of the most utilized two electron acceptors is DCIP, while one electron acceptors are usually cytochrome c, ABTS, Fe3+ and Mn3+ ions. During reduction of Fe3+ ions in the presence of molecular oxygen, H2O2 is formed and due to the Fenton reaction formation of hydroxyl radicals occurs. Due to this occurrence we wanted to use the Fenton reaction in order to develop a fluorescent assay based on the production of hydroxyl radicals and the fluorescence of aminophenyl fluorescein (APF). This would allow us to efficiently analyze cellobiose dehydrogenase gene libraries.With this fact in mind, the Fenton reaction was used to develop a fluorescent assay for the high throughput screening of cellobiose dehydrogenase genes, based on the detection of hydroxyl radicals with the fluorescent probe APF.The possible application of cellobiose dehydrogenase in the construction of various biosensors and biofuel cells is due the its ability to catalyze the oxidation of lactose, cellobiose and similar β – 1,4 – oligosaccharides do their corresponding lactones which then spontaneously hydrolyze to aldonic acids. Enzymes used in suchapplications need to satisfy certain criteria, such as exceptional sensitivity, substrate selectivity, stability and activity...

Интеракција молекула воде са ароматичним прстеновима има велики значај у многим системима, од биолошких молекула до материјала. Резултати истраживања ОН/π интеракција између течне воде и бензена показују да оне имају важну улогу у биолошким везивањима и препознавањима. Jачине интеракције између амонијака и ароматичних системима показале су да се NH/π интеракције могу узети у обзир при моделовању структура биолошких система.Поље изучавања ове докторске дисертације су нековалентне интеракције између молекула воде и амонијака са ароматичним системима, као и утицај координације воде, односно амонијака на поменуте интеракције. Када су у питању интеракције воде (некоординоване и координоване) са ароматичним прстеновима, испитиване су ОН/π и паралелне интеракције. Анализирани су подаци добијени из Кембричке базе структурних података (CSD) и подаци добијени на основу квантнохемијских прорачуна. Подаци добијени из CSD показују да су бројније паралелне од ОН/π интеракција, као и да су растојања између молекула воде и ароматичног прстена нешто краћа за координовану воду. Координација воде за јон метала утиче на јачину интеракција са ароматичним прстеном, интеракције аква комплекса су јаче. Прорачуни на MP2/def2-QZVP нивоу за систем H2O/C6H6 дају енергију ОН/π интеракције од -3,36 kcal/mol, док је за систем [Zn(H2O)6]2+/C6H6 она -13,96 kcal/mol. Координовани молекули воде преферирају паралелно-надоле оријентацију у односу на ароматичан прстен. Енергија ове интеракције за H2O/C6H6 систем је -3,11 kcal/mol, док је најјача израчуната интеракција -14,89 kcal/mol и односи се на систем [Zn(H2O)6]2+/C6H6.Координација амонијака за јон метала утиче на његове MLNH/π интеракције са бензеном. Координовани амонијак тежи приближавању арил-групи у односу на некоординовани амонијак. Енегрија NH/π интеракције за систем NH3/C6H6 износи -2,30 kcal/mol, док је за систем [Zn(NH3)6]2+/C6H6 она -14,77 kcal/mol. Квантнохемијски прорачуни показују слагање са закључцима добијеним на основу анализа крист, The interaction of water molecules with aromatic rings is of great importance in many systems, from biological molecules to materials. The results of the research on OH/π interactions of liquid water and benzene show that they have an important role in biological binding and recognition. The strength of the interactions between ammonia and aromatic systems have shown that NH/π interactions can be taken into consideration during the modeling of the structures of biological systems.This doctoral dissertation is in the field of non-covalent interactions between water and ammonia molecules with aromatic systems, as well as the influence of water and ammonia coordination on those interactions. To study the interactions between water (noncoordinated and coordinated) and aromatic rings, OH/π and parallel interactions have been examined. Data obtained from the Cambridge Structural Database (CSD) and data obtained on the basis of the quantum-chemical calculations have been analyzed. The data obtained from the CSD show that parallel interactions are more numerous than OH/π interactions. Coordination of water to a metal ion affects the strength of interactions with aromatic ring, the interactions of the aqua complexes are stronger. Calculations at MP2/def2-QZVP level of the OH/π interactions in water/benzene system yield the energy of -3.36 kcal/mol, while for the [Zn(H2O)6]2+/C6H6 system it is -13.96 kcal/mol. Coordinated water molecules prefer parallel-down orientation relative to the aromatic ring. The energy of this interaction for H2O/C6H6 system is -3.11 kcal/mol, while the strongest calculated interaction is -14.89 kcal/mol and it refers to the [Zn(H2O)6]2+/C6H6 system.Coordination of ammonia to a metal ion affects its MLNH/π interactions with benzene. Coordinated ammonia tends to approach the aryl group closer than noncoordinated ammonia. The energy of NH/π interaction for the NH3/C6H6 system is -2.30 kcal/mol, while for the system [Zn(NH3)6]2+/C6H6 it is -14.77 kcal/m

Интеракција молекула воде са ароматичним прстеновима има велики значај у многим системима, од биолошких молекула до материјала. Резултати истраживања ОН/π интеракција између течне воде и бензена показују да оне имају важну улогу у биолошким везивањима и препознавањима. Jачине интеракције између амонијака и ароматичних системима показале су да се NH/π интеракције могу узети у обзир при моделовању структура биолошких система. Поље изучавања ове докторске дисертације су нековалентне интеракције између молекула воде и амонијака са ароматичним системима, као и утицај координације воде, односно амонијака на поменуте интеракције. Када су у питању интеракције воде (некоординоване и координоване) са ароматичним прстеновима, испитиване су ОН/π и паралелне интеракције. Анализирани су подаци добијени из Кембричке базе структурних података (CSD) и подаци добијени на основу квантнохемијских прорачуна. Подаци добијени из CSD показују да су бројније паралелне од ОН/π интеракција, као и да су растојања између молекула воде и ароматичног прстена нешто краћа за координовану воду. Координација воде за јон метала утиче на јачину интеракција са ароматичним прстеном, интеракције аква комплекса су јаче. Прорачуни на MP2/def2-QZVP нивоу за систем H2O/C6H6 дају енергију ОН/π интеракције од -3,36 kcal/mol, док је за систем [Zn(H2O)6]2+/C6H6 она -13,96 kcal/mol. Координовани молекули воде преферирају паралелно-надоле оријентацију у односу на ароматичан прстен. Енергија ове интеракције за H2O/C6H6 систем је -3,11 kcal/mol, док је најјача израчуната интеракција -14,89 kcal/mol и односи се на систем [Zn(H2O)6]2+/C6H6. Координација амонијака за јон метала утиче на његове MLNH/π интеракције са бензеном. Координовани амонијак тежи приближавању арил-групи у односу на некоординовани амонијак. Енегрија NH/π интеракције за систем NH3/C6H6 износи -2,30 kcal/mol, док је за систем [Zn(NH3)6]2+/C6H6 она -14,77 kcal/mol. Квантнохемијски прорачуни показују слагање са закључцима добијеним на основу анализа кри, The interaction of water molecules with aromatic rings is of great importance in many systems, from biological molecules to materials. The results of the research on OH/π interactions of liquid water and benzene show that they have an important role in biological binding and recognition. The strength of the interactions between ammonia and aromatic systems have shown that NH/π interactions can be taken into consideration during the modeling of the structures of biological systems. This doctoral dissertation is in the field of non-covalent interactions between water and ammonia molecules with aromatic systems, as well as the influence of water and ammonia coordination on those interactions. To study the interactions between water (noncoordinated and coordinated) and aromatic rings, OH/π and parallel interactions have been examined. Data obtained from the Cambridge Structural Database (CSD) and data obtained on the basis of the quantum-chemical calculations have been analyzed. The data obtained from the CSD show that parallel interactions are more numerous than OH/π interactions. Coordination of water to a metal ion affects the strength of interactions with aromatic ring, the interactions of the aqua complexes are stronger. Calculations at MP2/def2-QZVP level of the OH/π interactions in water/benzene system yield the energy of -3.36 kcal/mol, while for the [Zn(H2O)6]2+/C6H6 system it is -13.96 kcal/mol. Coordinated water molecules prefer parallel-down orientation relative to the aromatic ring. The energy of this interaction for H2O/C6H6 system is -3.11 kcal/mol, while the strongest calculated interaction is -14.89 kcal/mol and it refers to the [Zn(H2O)6]2+/C6H6 system. Coordination of ammonia to a metal ion affects its MLNH/π interactions with benzene. Coordinated ammonia tends to approach the aryl group closer than noncoordinated ammonia. The energy of NH/π interaction for the NH3/C6H6 system is -2.30 kcal/mol, while for the system [Zn(NH3)6]2+/C6H6 it is -14.77 kcal

Derivatives of xylans were synthesized from corncob xylan by carboxymethylation, oxidization with different molar ratios of periodate (5, 10 15 and 20 mol%) and by reductive amination with tyramine. Modifications of tyramine carboxymethyl xylans (Tyr-CMX) were confirmed by FTIR, UV and NMR spectra. Concentration of ionizable groups increased from 1.5 mmol/g for carboxymethyl xylan (CMX) to 5.4 mmol/g for Tyr-CMX oxidized with 20 mol% of periodate. All Tyr-CMXs were able to form hydrogels the cross-linking reaction with horseradish peroxidase and peroxide. Tyr-CMXs were tested for amyloglucosidase (AG) encapsulation within hydrogel microbeads obtained in a reaction of emulsion polymerization with peroxidase. Average diameter of Tyr-CMX hydrogel microbeads was 52±25 µm and after encapsulation optimization with respect to the extent of CMX modification with tyramine, the concentration of Tyr-CMX, and the amount of added AG, microbeads with AG specific activity of 2 U/mL and 20% yield of immobilization were obtained. The optimum pH of the immobilized AG was not changed compared to the soluble one, while half-life at 60 °C was increased around 10 times. The Michaelis-Menten constant for the immobilized enzyme, 1.03 mM, was significantly lower than that for the soluble one, 1.54 mM. After 5 cycles of repetitive use in batch reactor, the immobilized AG retained 68% of initial activity.

In our previous study we demonstrated that proteinase PrtP is able to impair bacteriocin LcnB activity, despite being produced by the same organism and encoded by the same plasmid. However, precise mechanism of this action, i.e., the exact cleavage site within LcnB bacteriocin, as well as its effect on antimicrobial activity of the resulting peptide remained vague. Here we further explored the interplay between these two proteins and defined, using mass spectrometry, that this unusual hydrolysis indeed occurs in vivo, between the sixth and seventh amino acid on the N terminus of LcnB. To address whether the cleaved form of LcnB retains any level of activity, both recombinant and chemically synthesized variant of truncated LcnB were engineered and produced, but demonstrated no antimicrobial activity. When LcnB was recombinantly overexpressed and subjected to PrtP digestion, the change in its antimicrobial activity was monitored and the degradation products analyzed with reverse-phase high-pressure liquid chromatography. The results confirmed the inactivity of the truncated LcnB and additionally corroborated the PrtP cleavage site in LcnB bacteriocin. In addition, it was demonstrated that, once truncated, LcnB is not able to bind its receptor and is susceptible to additional hydrolysis. This is the first report on proteolytic inactivation of bacteriocins inside the same bacterial host.