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Diol dehydratase, dependent on coenzyme B12 (B12 -dDDH), displays a peculiar feature of being inactivated by its native substrate glycerol (GOL). Surprisingly, the isofunctional enzyme, B12 -independent glycerol dehydratase (B12 -iGDH), does not undergo suicide inactivation by GOL. Herein we present a series of QM/MM and MD calculations aimed at understanding the mechanisms of substrate-induced suicide inactivation in B12 -dDDH and that of resistance of B12 -iGDH to inactivation. We show that the first step in the enzymatic transformation of GOL, hydrogen abstraction, can occur from both ends of the substrate (either C1 or C3 of GOL). Whereas C1 abstraction in both enzymes leads to product formation, C3 abstraction in B12 -dDDH results in the formation of a low energy radical intermediate, which is effectively trapped within a deep well on the potential energy surface. The long lifetime of this radical intermediate likely enables its side reactions, leading to inactivation. In B12 -iGDH, by comparison, C3 abstraction is an endothermic step; consequently, the resultant radical intermediate is not of low energy, and the reverse process of reforming the reactant is possible.

Diol dehydratase, dependent on coenzyme B

We present a series of QM/MM calculations aimed at understanding the mechanism of the biological dehydration of glycerol. Strikingly and unusually, this process is catalyzed by two different radical enzymes, one of which is a coenzyme-B12-dependent enzyme and the other which is a coenzyme-B12-independent enzyme. We show that glycerol dehydration in the presence of the coenzyme-B12-dependent enzyme proceeds via a 1, 2-OH shift, which benefits from a significant catalytic reduction in the barrier. In contrast, the same reaction in the presence of the coenzyme-B12-independent enzyme is unlikely to involve the 1, 2-OH shift ; instead, a strong preference for direct loss of water from a radical intermediate is indicated. We show that this preference, and ultimately the evolution of such enzymes, is strongly linked with the reactivities of the species responsible for abstracting a hydrogen atom from the substrate. It appears that the hydrogen-reabstraction step involving the product-related radical is fundamental to the mechanistic preference. The unconventional 1, 2-OH shift seems to be required to generate a product-related radical of sufficient reactivity to cleave the relatively inactive C–H bond arising from the B12 cofactor. In the absence of B12, it is the relatively weak S–H bond of a cysteine residue that must be homolyzed. Such a transformation is much less demanding, and its inclusion apparently enables a simpler overall dehydration mechanism.

Molybdenum(VI) complexes of different nuclearity, mononuclear, [MoO2(L1 or 2) (MeOH)]MeOH (1MeOH and 2MeOH), [MoO2(L1 or 2)(D)] [D = pyridine, (1a and 2a), 3-methylpyridine, (1b and 2b) and 4-methylpyridine, (1c and 2c)], binuclear [{; ; ; ; MoO2(L1 or 2)}; ; ; ; 2(D)] (D = 4, 4'-bipyridine (1d, 1d' and 2d), and polynuclear complexes [MoO2(L1 or 2)]n (3 and 4) were synthesized by solution based reactions of enaminones (H2L1 = 3-(2-hydroxy-4- methylphenylamino)-1-phenylbut-2-en-1-one ; H2L2 = 3-(2- hydroxy-5-methylphenylamino)-1-phenylbut-2-en- 1-one) with the dioxobis(acetylacetonato)molybdenum( VI) complex, [MoO2(acac)2]. Reactions of the mononuclear complexes 1MeOH and 2MeOH with pyridine and its derivatives resulted in corresponding mononuclear [MoO2(L1 or 2)(D)] or binuclear [{; ; ; ; MoO2(L1 or 2)}; ; ; ; 2(D)] complexes. In case of [{; ; ; ; MoO2(L1)}; ; ; ; 2(4, 4-bpy)] two polymorphic forms are obtained (1d and 1d'). The cross-linked transformations of [MoO2(L1 or 2)(D)] complexes in solution or when exposed to vapors of N-heterocyclic bases have been explored. Crystal and molecular structures of ten complexes (1MeOH, 2MeOH, 1a–d, 1d' , 2b–d) were determined by the single-crystal X-ray diffraction analysis. Enaminone ligands and their molybdenum complexes were characterized by elemental and TG analysis, IR and NMR spectroscopy and screened for their in vitro cytotoxic and antibacterial activities. None of the tested compounds showed cytotoxic ability against THP-1 and HepG2 cell lines. Compounds 1MeOH, 1b, 2MeOH, 2a and 3, exhibited weak antibacterial activity on Moraxella catarrhalis strain while other complexes did not show antibacterial properties towards Staphylococcus aureus, Enterococcus faecalis and Escherichia coli bacteria.

In modern society, there is an increasing need to organize and fill the free time of children and young people. Observing and comparing the previous research on the free time of children and young people, it is evident that physical activity determined through sports is insufficiently practiced in the free time of children and young people. Youth sports games in the City of Zadar and Zadar County have been organized and held for many years, so they have proven to be promoters of a healthy lifestyle for children and youth. For the purposes of research and examination of respondents' satisfaction with the role and status of youth sports games in the City of Zadar and Zadar County, a survey method was used, where the sample consists of 467 participants in youth sports games, aged 12 to 18 for 2019 from the City Zadar and Zadar County. The aim of the research was to determine the degree of significance of youth sports competitions for participants and to directly determine the degree of socialization of that population caused by participation in competitions. According to the results of the research, it was determined that youth sports competitions are important for the participants, whose socialization in society has improved in accordance with the mentioned activity.

Molecular dynamics (MD) simulations have been employed for the first time to gain insight into the geometry of glycerol (GOL) bound within the active site of B12 -dependent diol dehydratase (B 12 -dDDH). A peculiar feature of the B 12 -dDDH enzyme is that it undergoes suicidal inactivation by the substrate glycerol. To fully understand the inactivation mechanism, it is crucial to identify all possible interactions between GOL and the surrounding amino acid residues in the enzyme−substrate complex. Particularly important is the orientation of the C3-OH group in GOL since the presence of this OH group is the only difference between GOL and propanediol (PDO), a substrate for B12 - dDDH that does not induce suicidal inactivation. The MD simulations indicate that glycerol can adopt two conformations that differ with respect to the orientation of the C3-OH group ; in one conformer, the C3-OH group is oriented toward Ser301 (C3-OH···Ser301), and in the other toward Asp335 (C3-OH··· Asp335). Although the former configuration is consistent with the crystal structure of B 12 -dDDH crystallized with cyanocobalamin (CNCbl) as the cofactor, MD simulations of this system suggest a substantial predominance of the latter conformer. A similar result with an even higher preference for the latter conformer is obtained for B 12 -dDDH with 5′-deoxyadenosylcobalamin (AdoCbl) as a cofactor. Employing QM/MM calculations it is found that the energy difference between the two conformers of GOL is very small in CNCbl B 12 -dDDH, where the slightly preferred conformer is C3-OH···Ser301. However, in AdoCbl B 12 -dDDH, this energy difference is higher, implying that GOL exists predominantly as the C3-OH···Asp335 conformer. These findings offer a new perspective for investigations of substrate-induced inactivation of the B 12 - dDDH enzyme.

We present a series of QM/MM calculations aimed at understanding the mechanism of the biological dehydration of glycerol. Strikingly and unusually, this process is catalyzed by two different radical enzymes, one of which is a coenzyme-B

Kompleksni spojevi molibdena (VI), [MoO2L(CH3OH)] (L = nesimetrične Schiffove baze), su priređeni sa svrhom proučavanja izmjena liganada u trans položaju odnosu na okso kisik MoO22+ skupine budući da su pogodni modelni sustavi za proučavanje katalitičkih reakcija. U literaturi je opisano katalitičko djelovanje ovog tipa kompleksa ali i njihova biokemijska svojstva pa se posljednjih godina intenzivno istražuje njihova potencijalna farmakološka primjena.1 U okviru ovog istraživanju priređeni su i indentificirani kompleksi s derivatima Schiffovih baza, dobivenih reakcijama 2-amino-4-metilfenola odnosno 2-amino-5-metilfenola i 1-benzil-1, 3-butadiona u etanolu (L1 = Bzac-4Me odnosno L2 = Bzac-5Me). Kompleksi molibdena(VI) su priređeni reakcijom bis(2, 4-pentandionato)dioksomolibdena(VI) i odgovarajuće Schiffove baze u metanolu. Molekulska i kristalna struktura kompleksa [MoO2L1(CH3OH)] i [MoO2L2(CH3OH)] su određene na temelju podataka rentgenske strukturne analize, infracrvene spektroskopije, elementne i termičke analize. Ispitivanja svojstava priređenih kompleksa su pokazala da je moguća izmjena koordiniranog metanola s drugim ligandima kao što su piridin, 4-metilpiridin, 4, 4-bipiridin i imidazol u otopini i u čvrstom stanju. Ustanovljeno je također da u odsutnosti koordinirajućeg liganda kao što je alkohol ili neka N-baza dolazi do polimerizacije i nastanka [MoO2L]n kompleksa. Izmjena O- i N-donorskih liganada kao i polimerizacija su popraćene promjenom boje.

The aim of this study was to compare osteotomy for malunited distal radius fracture with embedment of a corticospongious graft into a periosteal flap of the recipient bone (test) with the standard procedure (control) with respect to graft resorption. A retrospective assessor-blind analysis of consecutive patients (test: n = 19, control: n = 30) was performed. Ulnar tilt, palmar tilt and capitate-ulna distance were assessed from radiographs taken before, two to four days after and over three months after the surgery to determine loss of correction achieved by the surgery and estimate graft resorption during the postoperative period. In both unadjusted and adjusted comparisons, loss of correction of all parameters was lower in the test group (P