GENDER DIFFERENCES IN CHESS PERFORMANCE

Women are underrepresented and underperformanced in chess at the top level. An explanation for the small number of female chess players because chess is an intellectually demanding activity would support the view of biological gender differences in intellectual abilities. However, despite different theories, there is no scientific evidence for sex specific intellectual performance differences. Furthermore, memory is heavily implicated in chess performance and is also often used to explain sex differences. Many novel findings are emerging and complementing cognitively-oriented research on chess. Sex stereotypes can have a greatly debilitating effect on female players leading to a sharp decline in performance when competing with males in chess. Women generally score lower than men both on aggressiveness and dominance and at the same time during a chess game, mental fatigue occurs earlier in women. This is usually explained by the fact that in the female body glycogen content is lower compared to males due to hormonal conditions and therefore unable to meet the demands for fast energy. Women also seem disadvantaged because they approach chess competitions with less confidence and with a more cautious attitude than their male counterparts. A motivational perspective may be better suited for understanding the underperformance of women as chess players. Studies of psychology, physiology and biochemistry of chess players should be used to improve the practice and pedagogy for male and female chess players

Enzymatic synthesis of vitamin B6 precursor

3-Cyano-4-ethoxymethyl-6-methyl-2-pyridone is an important precursor in the synthesis of vitamin B6, obtained in the addition reaction between 2-cyanoacetamide and 1-ethoxy-2,4-pentanedione catalyzed by lipase from Candida rugosa (triacylglycerol ester hydrolases, EC 3.1.1.3). This work shows new experimental data and mathematical modeling of lipase catalyzed synthesis of 3-cyano-4-ethoxymethyl-6-methyl-2-pyridone, starting from 1-ethoxy-2,4-pentanedione and 2-cyanoacetamide. Kinetic measurements were done at 50 oC with enzyme concentration of 1.2 % w/v. Experimental results were fitted with two kinetic models: the ordered bi-ter and ping-pong bi-ter model, and the initial rates of the reaction were found to correlate best with a ping-pong bi-ter mechanism with inhibition by 2-cyanoacetamide. Obtained specificity constants indicated that lipase from C. rugosa had higher affinity towards 1-ethoxy-2,4-pentanedione and less bulky substrates. [Projekat Ministarstva nauke Republike Srbije, br. 172013, br. III 46010 and br. 172049

CHANGES IN SPEED, AGILITY AND BODY COMPOSITION OF TOP-RANKED FEMALE HANDBALL PLAYERS DURING THE PLAYING SEASON

Handball is a dynamic Olympic sport dominated by acyclic movements (sudden changes in direction, jumps, landings, contacts between the players, etc.) with speed and agility playing an important role in their successful realization. Our aim was to establish which changes occurred in the body composition, speed and agility of top-ranked female handball players during the playing season. The parameters for estimating body composition were: body mass, body mass index (BMI), the percentage of muscle and fat. The ability to achieve speed (in 5, 10 and 30m sprints) and agility (new envelope test without a ball, straight slalom run without a ball and Straight slalom run with a ball, zig-zag with and zig-zag without a ball) was estimated with the portable timing system. The differences between the initial and the final measurements were established with the Student’s t-test. The results obtained show that there were statistically significant changes and weaker results in almost all the tested variables. The only improvements were detected in the maximum speed in 30m sprint and the agility without a ball (new envelope test and slalom run without a ball). It is recommended that the training plan should be carefully devised (the activities of the high intensity load should be applied throughout the season) as well as the plan for proper sports nutrition (body mass should be reduced with simultaneous increase in the muscular mass component)

Izolovanje izoformi lipaze iz Candida rugosa

The yeast Candida rugosa is a convenient source of lipases for science and industry. Crude preparation of Candida rugosa lipase (CRL) consists of several extracellular lipases. Isoenzyme profile depends on the culture or fermentation conditions. All isoforms are coded by the lip pseudogene family; they are monomers of 534 amino acids and molecular weight of about 60 kDa. They share the same catalytic mechanism and interfacial mode of activation. Isoenzymes differ in isoelectric points, post-translational modifications, substrate specificity and hydrophobicity. The presence of different lipase isoforms and other substances (i.e., inhibitors) in crude preparation leads to lack of their productivity in biocatalytic reactions. Purification of specific isoform improves its overall performance and stability. This paper provides an overview of different methods for purification of CRL isoenzymes up to date, their advantages and disadvantages.Lipaze (hidrolaze estara glicerola, E.C.3.1.3.3) su važna grupa enzima, široko rasprostranjenih u prirodi. Mogu se izolovati iz materijala biljnog, životinjskog ili mikrobnog porekla. Zahvaljujući svojim karakteristikama, pobuđuju sve više pažnje kao efikasni biokatalizatori u različitim sintetičkim i hidrolitičkim procesima. Među lipazama, poreklom iz mikroorganizama, posebno su značajne one koje produkuje kvasac Candida rugosa. Komercijalni preparat lipaza iz C. rugosa može sadržati 5-7 izoformi ekstracelularnih lipaza. Sve te izoforme kodirane su od strane lip familije pseudogena, a na njihovu ekspresiju utiču uslovi u kojima se mikroorganizam gaji (sastav hranljive podloge je najvažniji). Ekstracelularne lipaze, koje proizvodi C. rugosa su monomerni glikoproteini, molekulske mase od oko 60 kDa, sa 534 aminokiseline. Za sve izoforme je karakterističan isti složeni mehanizam aktivacije na granici faza i mehanizam katalize, kakav se sreće i kod serin-proteaza. Izoenzimi se međusobno razlikuju po post-translacionim modifikacijama (udelu ugljohidratne komponente), supstratnoj specifičnosti, izoelektričnim tačkama i hidrofobnosti. Prisustvo više izoformi lipaza u komercijalnom preparatu utiče na njihovu produktivnost u reakcijama koje katalizuju. Takvi preparati često sadrže i druge supstance koje mogu uticati na aktivnost enzima (na primer inhibitore). Razdvajanjem pojedinačnih izoformi iz komercijalnog preparata poboljšavaju se njihova enantioselektivnost, specifična aktivnost i stabilnost enzima, što je od izuzetnog značaja za njihovu dalju primenu. U ovom radu su predstavljeni različiti pristupi u razdvajanju pojedinačnih izoformi vanćelijskih lipaza iz komercijalnog preparata C. rugosa, njihove prednosti i nedostaci

Proizvodnja lipaze iz Pseudozyma aphidis i utvrđivanje aktivnosti i stabilnosti lipaze u polarnim organskim rastvaračima

The production of lipase from Pseudozyma aphidis (DSM 70725) was determined in six different media. The highest lipase production was observed in a medium with glucose as the sole carbon source, and yeast extract and sodium nitrate as the nitrogen sources. The time course studies of growth and lipase production in the optimal medium revealed that the highest lipase production was achieved at the end of the log phase of growth, reaching the value of 35.0 U cm(-3) in the fifth day of cultivation. The effects of various polar, water-miscible, organic solvents on the activity and stability of the crude lipase produced by P. aphidis were evaluated. The hydrolytic activity of the crude lipase towards p-nitrophenyl palmitate (p-NPP) in aqueous media and in organic solvents was determined, using the same spectrophotometric assay in both the aqueous and organic media. The crude lipase preparation exhibited activity towards p-NPP only in acetone and acetonitrile, while the lipase was stable only in acetone, with 23 % residual activity after 24 h of incubation. These results suggested that lipase from P. aphidis can be used as a biocatalyst for potential applications in such organic solvents.Proizvodnja lipaze iz Pseudozyma aphidis utvrđena je u šest različitih medijuma. Najviša proizvodnja uočena je u medijumu gde je glukoza bila izvor ugljenika, a ekstrakt kvasca i natrijum-nitrat izvori azota. Praćenjem dinamike rasta i proizvodnje lipaze u optimalnom medijumu, uočeno je da se najviša proizvodnja lipaze dostiže pred kraj logaritamske faze rasta, i dostiže vrednost od 35 U cm-3 u petom danu kultivacije, što je četri puta veća proizvodnja od one do sada prijavljene u literaturi. Utvrđen je efekat različitih polarnih organskih rastvarača, mešljivih sa vodom, na aktivnost i stabilnost lipaze iz P. aphidis. Hidrolitička aktivnost lipaze prema para-nitrofenil-palmitatu (p-NPP-u) u vo- denoj sredini i organskim rastvaračima utvrđena je upotrebom istog spektrofotometrijskog testa. Pokazano je da lipaza ima aktivnost prema p-NPP-u samo u acetonu i acetonitrilu, dok je enzim stabilan jedino u acetonu i zadržava 23% aktivnosti nakon 24 časa inkubacije. Dobijeni rezultati ukazuju da lipaza iz P. aphidis može biti korišćena kao biokatalizator za potencijalne primene u acetonu kao medijumu

Supplementary data for the article: Nesic, A. R.; Trifunovic, S. S.; Grujic, A. S.; Velickovic, S. J.; Antonovic, D. G. Complexation of Amidated Pectin with Poly(Itaconic Acid) as a Polycarboxylic Polymer Model Compound. Carbohydrate Research 2011, 346 (15), 2463–2468. https://doi.org/10.1016/j.carres.2011.08.021

Supplementary material for: [https://doi.org/10.1016/j.carres.2011.08.021]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1219

Stabilizacija lipaza iz Candida rugosa jednostavnom i efikasnom imobilizacijom na hidroksiapatitu

Razvili smo brz i efikasan metod imobilizacije industrijski veoma vrednih Candida rugosa lipaza (CRL) na ekonomičan, biokompatibilan nosač - hidroksiapatit, sa visokim prinosom imobilizacije (blizu 100 %) i prinosom aktivnosti od 50 %. Imobilizovane lipaze su pokazale značajno višu stabilnost nego slobodni enzim, nakon termalnog tretmana na 60 oC i u prisustvu različitih 95 % polarnih organskih rastvarača, pre svega kratkolančanih alifatičnih alkohola, značajnih polaznih sirovina u sintezi brojnih estara i drugih značajnih proizvoda. Predstavljeni rezultati ukazuju na veliki upotrebni potencijal dobijenog preparata u različitim industrijskim procesima, koji iziskuju rad u nekonvencionalnim reakcionim uslovima.We have developed a simple and highly effective method for immobilising industrially very appreciated and valuable Candida rugosa lipases from commercial preparation on ecologically suitable, biodegradable and economical hydroxyapatite support. Our immobilisation protocol resulted in excellent immobilisation yield of nearly 100 % and activity yield of 50 %, which is significantly higher in comparison to other immobilisation protocols for different enzymes on the same support. Immobilised lipase formulation has proven to have superior stability, compared to free enzyme, at both high temperature (60 o C) and in the presence of different polar organic solvents, especially short-chain alcohols: methanol, ethanol and iso-propanol. Therefore, presented experimental data strongly support the great future potential of the prepared Candida rugosa immobilisat