RATKO M. JANKOV

University of Belgrade, Belgrade, SE, Serbia

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Publications (40)91.99 Total impact

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    ABSTRACT: Higher plants possess several mechanisms of defense against plant pathogens. Proteins actively synthesized in response to those stresses are called defense-related proteins which, among others, include certain protease inhibitors. It is of particular relevance to investigate plant natural defense mechanisms for pathogen control which include cystatins-specific inhibitors of cysteine proteases. In this study, a cysteine proteinase inhibitor (CPI), 11 kDa in size, was purified from green kiwifruit to homogeneity. Immuno-tissue print results indicated that CPI is most abundant in the outer layer of pericarp, near the peel, and the inner most part of the pulp-sites where it could act as a natural barrier against pathogens entering the fruit. The purified protein (15 µmol L(-1) ) showed antifungal activity against two phytopathogenic fungi (Alternaria radicina and Botrytis cinerea) by inhibiting fungal spore germination. In vivo, CPI (10 µmol L(-1) ) was able to prevent artificial infection of apple and carrot with spore suspension of B. cinerea and A. radicina, respectively. It also exerted activity on both intracellular and fermentation fluid proteinases. Identification and characterization of plant defense molecules is the first step towards creation of improved methods for pathogen control based on naturally occurring molecules. Copyright © 2012 Society of Chemical Industry.
    Journal of the Science of Food and Agriculture 06/2012; 92(15):3072-8. · 1.76 Impact Factor
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    ABSTRACT: The conditions required for the isolation of high quality total RNA from European linden (Tilia cordata) leaves and pollen were determined. Pure total RNA was isolated from linden leaves utilizing a Qiagen plant mini kit, while the total RNA isolated from linden pollen using this method was degraded. Successful isolation of total RNA from both linden pollen and leaves, however, was achieved following TRIzol™ preparation of the total RNA. The total RNA isolated using TRIzol™ was contaminated with genomic DNA but treatment with the enzyme DNase, in solution or on-column, efficiently removed the genomic DNA. Furthermore, the conditions for the elimination of genomic DNA contamination on-column and isolation of pure total RNA from leaves were optimized. The isolated total RNA from both leaves and pollen was used successfully in first- and second-strand cDNA synthesis reactions and in a reverse transcription polymerase chain reaction (RT-PCR), demonstrating that the total RNA isolated using this method was functional. In conclusion, pure and functional total RNA from T. cordata leaves and pollen (27.8±7.9 µg g-1 leaves; 25.7±1.1 µg g-1 pollen) could be obtained and was suitable for application in further molecular biology studies.
    Journal of the Serbian Chemical Society 01/2012; · 0.91 Impact Factor
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    ABSTRACT: Lipase A from Candida antarctica (CAL A) was purified to apparent homogeneity in a single step using hydroxyapatite (HAP) chromatography. CAL A bound to HAP was eluted with 10mM Na-phosphate buffer, pH 7.0 containing 0.5% Triton X-100. The protocol resulted in a 3.74-fold purification with 94.7% final recovery and 400.83 U/mg specific activity. Silver staining after SDS-PAGE revealed the presence a single band of 45 kDa. The enzyme exhibited a temperature optimum of 60°C, was unaffected by monovalent metal ions, but was destabilized by divalent metal ions (Zn(2+), Ca(2+), Mg(2+), Cu(2+), Mn(2+)) and stimulated by 50mM Fe(2+). Detergents at 0.1% concentrations did not affect lipase activity. Except for Triton X-100, detergent concentrations of 1% had a destabilizing effect.
    Bioresource Technology 12/2011; 107:358-62. · 5.04 Impact Factor
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    ABSTRACT: In this report, α-isosalicin, a potent anticoagulant and skin whitening agent, was synthesized by a highly efficient chemoselective and diastereoselective reaction, catalyzed by maltase from bakers’ yeast (Saccharomyces cerevisiae). The highest yield of this one-step transglucosylation reaction was achieved with 50 mM of salicyl alcohol as a glucose acceptor. The key reaction factors were optimized using response surface methodology (RSM) with an enzyme concentration of 10 U/mL. The optimum temperature of the reaction was determined as 36.5 °C, the optimal maltose concentration was 40% (w/v), the optimal pH was 6.5, and the optimal reaction time was 16 h. Under these conditions 75% of α-isosalicin was obtained, with a yield of 10 g/L, and no by product formation was observed.
    Process Biochemistry. 08/2011; 46(8):1698–1702.
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    Journal of the Serbian Chemical Society 01/2011; 76(6):847-855. · 0.91 Impact Factor
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    ABSTRACT: In this study, exopolysaccharide (EPS) produced by an extremophylic strain of Pseudomonas aeruginosa san-ai was used as a support for immobilization of lipase produced together with EPS, using new and simple, single step procedure. The highest EPS production (36.5 mg L−1) was observed in the Luria Bertani (LB) medium supplemented with sunflower oil and Tween 80. The EPS structure was analyzed by FT-IR and 1H NMR, and it was found that EPS from P. aeruginosa is of the alginate type. Lipase, produced by the same strain was entrapped in Ca–EPS beads, formed by dripping a concentrated culture supernatant in CaCl2 solutions. Effects of immobilization conditions on loading efficiency and immobilization yield were investigated, and the potential for reuse of immobilized lipase was monitored. It was shown that the immobilized enzyme could be used for up to three reaction cycles, after which 77% of activity was retained.
    Carbohydrate Polymers 01/2011; 83(3):1397-1401. · 3.48 Impact Factor
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    ABSTRACT: Kiwifruit has become a frequent cause of fruit allergy in the recent years. The molecular basis of type I hypersensitivity to kiwifruit is attributed to 11 IUIS allergens, with Act d 1, Act d 2 and Act d 5 characterized in extenso. Evaluation of the allergenic properties of Act d 4, a cysteine proteinase inhibitor from green kiwifruit (Actinidia deliciosa) was performed in this study. Identity of the purified glycoprotein was determined by Edman degradation and by mass fingerprint whereby more than 90% of the primary structure of the mature kiwifruit cystatin was confirmed. Using MALDI TOF analysis, molecular masses of 10902.5 and 11055.2 Da were detected for Act d 4, respectively. Positive skin prick reactivity with Act d 4 was induced in three kiwifruit allergic patients, as well as the upregulation of CD63 and CD203c molecules in the basophile activation assay. The IgE reactivity was detected in dot blot analysis while Western blot analysis was negative using sera from six kiwifruit patients, suggesting the presence of conformational IgE epitopes on the Act d 4 molecule. As activator of effector cells in type I hypersensitivity Act d 4 is a functional allergen contributing to the clinical symptoms of kiwifruit allergy.
    Molecular Nutrition & Food Research 11/2009; 54(3):373-80. · 4.31 Impact Factor
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    ABSTRACT: Lectins are widely used in many types of assay but some lectins such as banana lectin (BanLec) are recognised as potent immunostimulators. Although BanLec's structure and binding characteristics are now familiar, its immunostimulatory potential has not yet been fully explored. The synthesis by recombinant technology of a BanLec isoform (rBanLec) whose binding properties are similar to its natural counterpart has made it possible to overcome the twin problems of natural BanLec's microheterogeneity and low availability. This study's aim is to explore the immunostimulatory potential of rBanLec in the murine model. Analyses of the responses of Balb/c- and C57 BL/6-originated splenocytes to in vitro rBanLec stimulation were performed to examine the dependency of rBanLec's immunostimulatory potential upon the splenocytes' genetic background. It is shown that the responses of Balb/c- and C57 BL/6-originated splenocytes to rBanLec stimulation differ both qualitatively and in intensity. The hallmarks of the induced responses are T lymphocyte proliferation and intensive interferon-gamma secretion. Both phenomena are more marked in Balb/c-originated cultures; Balb/c-originated lymphocytes produce interleukin (IL)-4 and IL-10 following rBanLec stimulation. Our results demonstrate that any responses to rBanLec stimulation are highly dependent upon genetic background; they suggest that genetic background must be an important consideration in any further investigations using animal models or when exploring rBanLec's potential human applications.
    International immunopharmacology 10/2009; 10(1):120-9. · 2.21 Impact Factor
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    ABSTRACT: This study focuses on the isolation and characterization of a peptide with bacteriocin-like properties isolated from Lactobacillus rhamnosus strain 68, previously identified by 16S rRNA gene sequencing and originating from human gastrointestinal flora. The peptide was isolated from a supernatant of bacteria maintained under restrictive conditions by a combination of ethanol precipitation and reversed-phase chromatography. The molecular mass of the peptide as assessed by mass spectrometry was 6433.8 Da. An isoelectric point of 9.8 was determined by 2D-PAGE. The peptide designated rhamnosin A inhibited Micrococcus lysodeikticus ATCC 4698 but did not inhibit Lactobacillus plantarum 8014 or Lact. plantarum 39268. Inhibitory activity against M. lysodeikticus at concentrations used in this study was shown to be bacteriostatic rather than bacteriolytic or bactericidal. Rhamnosin A retained biological activity after heat treatment (95 degrees C, 30 min) but was sensitive to proteolytic activity of pepsin and trypsin. The N-terminal sequence of rhamnosin A, as determined by Edman degradation and in more detail by blast analysis, did not show identity with any currently available Lact. rhamnosus HN001-translated protein sequences, nor any significant similarity with other sequences in the nonredundant protein sequence database. Being a small, heat-stable, nonlanthionine-containing peptide, rhamnosin A should be categorized as a class II bacteriocin. This study describes a partial bacteriocin sequence isolated from Lact. rhamnosus 68 and broadens our understanding of bacteriocins.
    Journal of Applied Microbiology 08/2009; 107(6):2108-15. · 2.20 Impact Factor
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    ABSTRACT: The activity of α-glucosidase from baker's yeast was determined in various concentrations of dioxan, tetrahydrofuran, tert-butanol, dimethylformamide, methanol and dimethylsulfoxide (DMSO). Higher activities were observed with sucrose than with nitrophenylglucoside as substrate in cosolvent mixtures. In 30% (v/v) DMSO, 25% of the activity obtained in pure water was detected, and in 30% (v/v) methanol 12.5% of the activity in pure water was detected, while in other cosolvents there was almost no activity under these conditions. α-glucosidase was immobilized onto a macroporous copolymer of ethylene glycol dimethacrylate and glycidyl methacrylate, poly(GMA-co-EGDMA), by the glutaraldehyde method. By immobilization, the half-life of the enzyme in 35% (v/v) methanol was increased from 6 to 60 min and from 4 to 15 min in 45% (v/v) DMSO. The activity of the immobilized enzyme in 30% (v/v) DMSO and 30% (v/v) methanol was 22% and 18% of the activity in pure water, respectively.
    07/2009; 24(3):195-200.
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    ABSTRACT: Treating allergies with modified allergens is an approach to make the treatment safer and more efficient. Art v 1 is the most prominent allergen of mugwort pollen and a significant cause of hayfever around Europe. The aim of this study was to reduce the allergenicity of Art v 1 by acetylation, and to investigate the capacity of the modified protein to generate blocking antibodies. The reduction of allergenicity of Art v 1 following acetylation was monitored by immunoblot, ELISA inhibition using a pool of sera from mugwort pollen allergic patients, basophil activation assay and by skin prick testing of mugwort-allergic patients. Rabbits were immunized against Art v 1 and acetylated Art v 1 (acArt v 1) and the rabbit antisera were tested for their capacity to block human IgE binding in ELISA. Human T cell proliferation against Art v 1 and acArt v 1 was examined in peripheral blood mononuclear cells (PBMCs) of mugwort pollen allergic patients and cytokine release in PBMC cultures was monitored. Acetylation of Art v 1 gave a derivative of reduced allergenicity in the in vitro and ex vivo tests applied. The skin test reactivity to acArt v 1 was significantly reduced in 19 patients when compared with the reactivity to Art v 1. Rabbit antibodies to acArt v 1 and Art v 1 showed similar capacity to block human IgE binding to Art v 1 in inhibition ELISA. Both proteins were able to induce proliferation of PBMCs and CD3/CD4(+) cells of mugwort-allergic patients. Release of IL-5 was significantly reduced in cultures stimulated with acArt v 1. Art v 1 modified by acetylation had a significantly reduced allergenicity in vitro and in vivo, while its immunogenicity was retained. Modification of allergens by acetylation could be a new strategy for allergen-specific immunotherapy.
    Clinical & Experimental Allergy 02/2009; 39(3):435-46. · 4.79 Impact Factor
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    ABSTRACT: House dust mites (HDM) represent a major source of allergens, contributing to the increasing incidence of type I hypersensitivity disease worldwide. Over 30 different IgE-binding proteins from the HDM extract were detected. Although group 1 and 2 have been identified as major allergens, due to the safety and efficacy of allergy diagnosis and immunotherapy, there is a need to carefully evaluate the clinical relevance of other allergens present in the HDM extract. In regard to this, a high molecular mass allergen of about 68 kD was purified from the HDM extract using a combination of gel permeation chromatography and reversed-phase chromatography. The IgG and IgE reactivity of the purified protein were preserved during the purification process, as confirmed by Western blot analysis with polyclonal rabbit antibodies and dot blot analysis with a pool of sera from subjects with house dust mite allergy, respectively. In addition, the IgE reactivity was confirmed using ELISA testing with nine patient sera. The biological potency of the 68 kD allergen was confirmed by skin prick testing in five allergic subjects, suggesting that the high molecular mass allergen is a good candidate for component-resolved diagnosis of house dust mite allergy and eventual therapeutic treatment.
    Journal of the Serbian Chemical Society. 01/2009;
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    Tanja Cirkovic Velickovic, Ratko M Jankov
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    ABSTRACT: Specific immunotherapy is a clinically effective causative treatment for allergic conditions. However, the reagents used for immunotherapy are crude extracts, prepared from natural sources, and as such may cause potential life-threatening anaphylactic side effects. Our increasing knowledge of mechanisms that lead to allergy and of the mechanisms of successful immunotherapy have introduced new ideas for the treatment of allergic diseases. Techniques of biochemistry and molecular biology have made it feasible to design novel therapeutic approaches for improved and safer forms of allergen-specific immunotherapy. The purpose of this review is to examine different approaches in designing novel allergen formulations for specific immunotherapy. These include chemically modified forms of allergens, genetically modified allergens (hypoallergens), hybrid allergens and allergens bearing immunostimulatory molecules, or adjuvants, which foster Th 1 immune responses. There is great interest in newly designed allergens and their derivatives to improve the efficacy and safety of allergen immunotherapy. A better understanding of immunological mechanisms and further clinical trials utilizing new allergen formulations are needed.
    Inflammation & Allergy - Drug Targets (Formerly ?Current Drug Targets - Inflammation & Allergy) 01/2009; 7(4):270-8.
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    ABSTRACT: The use of enzymes may improve the functional properties of various food ingredients. The aim of this study was to examine the effects of proteolytic contaminants in phenol oxidases on β-lactoglobulin (BLG). In the presence of Trametes versicolor laccase and Agaricus bisporus tyrosinase, both variants of BLG (A and B) underwent removal of a peptide from the N-terminus. The truncated forms were more susceptible to digestion by pepsin. The truncation of BLG resulted from contaminating proteases and not due to the action of phenol oxidases. The removal of N-terminal peptides proceeded quickly, while the rest of the globular protein remained resistant to proteolysis for up to 3 h. In the case of the application of enzymes in food bioprocessing, it may be important to carefully monitor the effects of contaminating proteases in enzyme preparations used.
    International Dairy Journal. 01/2009;
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    ABSTRACT: Art v 1 is the major allergen of mugwort (Artemisia vulgaris) pollen, a significant cause of hay fever all over Europe. Specific immunotherapy is the only treatment modality for allergic disease. Application of modified allergens makes the treatment safer and more efficient. In this work, two out of three (citraconic anhydride, cis-aconitic anhydride, 2,3-dimethylmaleic anhydride) tested anhydrides were proven to be suitable for chemical modifications of allergens. Art v 1 was modified by cis-aconitylation and citraconylation in order to obtain derivatives of Art v 1 that may be suitable for further immunological testing. Acylation of Art v 1 gave derivatives (caaArt v 1 and citArt v 1) with about 80 % modified amino groups. The derivatives were in the monomeric form and had dramatically reduced pI values. Both derivatives were relatively stable at neutral pH values, while the acyl groups undergo hydrolysis under acidic conditions. Modification of allergens by cis-aconitylation and citraconylation could be a new tool for obtaining allergoids.
    Journal of the Serbian Chemical Society. 01/2009;
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    ABSTRACT: BACKGROUND: It is thought that food sensitisers must be able to reach the intestine in order to sensitise patients. Pectin is a gel-forming plant polysaccharide that can protect allergens from in vivo gastric digestion and in vitro pepsin digestion. The aim of this study was to examine if pectin gel formed in the acidic environment of the stomach can protect labile allergen from in vitro gastrointestinal digestion.RESULTS: Pectin forms a gel in the acidic conditions of gastric fluid up to a concentration of 1.0 ± 0.14 g L−1. Four allergenic fruits (kiwi, cherry, apple and banana) form gels in the same manner at the dilutions 14.8 ± 0.4; 8.4 ± 0.2, 9.4 ± 0.35 and 29.1 ± 0.2, respectively. The time necessary for dissolution of 50 g L−1 pectin gel in intestinal fluid was found to be 70 ± 0.2 min. Pectin gel formed in situ was able to protect Act c 1 from pepsin digestion for 1 h and from further intestinal digestion for one additional hour.CONCLUSION: Pectin gel in an acidic environment protects Act c 1 from pepsin digestion and dissolves slowly in the slightly basic environment of the intestine allowing the survival of fruit allergen for additional time and possible interaction with the gut immune system. Copyright © 2008 Society of Chemical Industry
    Journal of the Science of Food and Agriculture 10/2008; 89(1):8 - 14. · 1.76 Impact Factor
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    ABSTRACT: Thaumatin-like proteins (TLPs) have been established as a new family of fruit and pollen allergens. The aim of this study was to develop a two-site ELISA for the quantification of the thaumatin-like kiwi allergen (Act d 2) in kiwifruit extracts and kiwifruit-containing food products. Genomic DNA (gDNA) of Act d 2 was amplified and the deduced amino acid sequence was determined to obtain a primary structure. Act d 2 purified from kiwifruit extract by HPLC was identified by Edman degradation and MS. Balb/c mice were immunized with Act d 2 for the production of mAbs by hybridoma technology. The optimized ELISA measured Act d 2 concentrations ranging from 0.2 to 9.0 ng/mL, with intra- and interassay coefficients of variation of 3.65 and 10.44%, respectively. The developed ELISA is a useful method for the quantification of the thaumatin-like kiwi allergen in kiwifruit extracts as well as the allergen level in kiwifruit-containing food products. It may be a helpful analytical tool for the evaluation of the stability (integrity) of fruit allergen extracts for in vitro diagnosis.
    Molecular Nutrition & Food Research 07/2008; 52(6):701-7. · 4.31 Impact Factor
  • Journal of Biotechnology - J BIOTECHNOL. 01/2008; 136.
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    ABSTRACT: A simple ion-exchange HPLC-UV method was developed for determination of major allergens from mugwort pollen and kiwi fruit extracts in mass-units. The separation of Art v 1 and Act c 1 from other components in the extracts was achieved in one step. The extinction coefficients used in the study were theoretically determined and compared to the extinction coefficients determined by gravimetry. We also reported a close correlation of the major allergen contents with the overall allergenic potency of the extracts determined by inhibition ELISA. This method could be a useful tool for standardization of allergenic extracts for clinical use.
    Journal of Chromatography B 11/2007; 857(2):188-94. · 2.49 Impact Factor
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    ABSTRACT: 4-Hydroxyphenyl-β-isomaltoside has been synthesized by α-glucosidase assisted transglycosylation between arbutin as acceptor and sucrose as donor molecules, respectively. Optimum conditions for the transglucosylation reaction were 40 °C for 20 h with 10 mM arbutin and 1.5 M sucrose in a 100 mM sodium citrate/phosphate buffer at pH 5.0. The new glucoside was obtained in a 50% molar yield with respect to arbutin.
    Tetrahedron Letters 10/2007; 48(40):7222–7224. · 2.40 Impact Factor

Publication Stats

141 Citations
91.99 Total Impact Points

Institutions

  • 1996–2009
    • University of Belgrade
      • Faculty of Chemistry
      Belgrade, SE, Serbia
  • 1997–1999
    • Faculty of Music in Belgrade
      Beograd, Central Serbia, Serbia