Wyniki wyszukiwania - Biblioteka Nauki

1

Mechanizm i kinetyka procesów tworzenia oraz zaniku ekscymerów XeCl* w układach Xe-RCl

100%

Wojciechowski K.

Wiadomości Chemiczne

|

1998

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tom [Z] 52, 5-6

405-429

EN

The mechanism and kinetics of decay of excited Xe(6s[3/2]1,2) atoms formed by irradiation of pure Xe by xenon resonance light (l = 147 nm) is presented basing on Moutard et al. [9] reaction scheme (r.(2)-(8)). The mechanism of the decay of higher xenon excited states (6p, 6d, ...) produced by the electron beam is also presented (r.(9)-(14)). On this basis the mechanism and kinetics of energy transfer processes to RCl molecules in Xe-RCl system leading to XeCl(B,C) excimers is discussed. In particular the mechanism and kinetics of two-and three-body reactions of the lowest Xe(6s[3/2]1) state with chlorine donor molecules is presented. It has been shown that the two-body energy transfer reactions (19) occur with the rate constants in the range (3.5-7)ˇ10-10 cm3 ˇs-1 [10, 11, 32, 33] (Tabs.1,2). The yield of XeCl* excimers in these reactions is in the range from 0.02 for HCl up to 1.0 for Cl2 molecule (Tabs 1,2). It has been shown also that at higher xenon pressures (above 20-50 Torr) with reaction (19) competes the fast three-body reaction (23), which also is a source of XeCl* excimers [10, 11]. The rate constants of reaction (23) for a few molecules are shown in Tab. 2. They are in the range (1-2)ˇ10-28 cm6 ˇs-1 and the yields of XeCl* excimers produced in these reactions are from 0.19 for CCl4 up to 0.5 for PCl3. It seems to be important in the construction of excimer lasers that in the case of HCl molecule, often used as a source of XeCl* excimers, the rate constant of three-body energy transfer reaction (23) is extremely high, k23 = 2.2ˇ10-27 cm6ˇs-1 [10] and the yield of XeCl* excimersin this process is equal to zero [10]. The XeCl* excimers decay via fluorescence with the maximum at l =308 nm, for B-X transition and l = 340 nm for C-A transition. The typical spectrum of XeCl* excimers fluorescence is shown in Fig. 5. The fluorescence lifetime (r. (31), (32)) of XeCl* excimers is equal to 11 and 120-130 ns, for B-X and C-A transitions, respectively [46, 58]. There is shown that the above values of XeCl* excimers lifetimes concern excimers at the lowest vibrational level (v = 0) and they increase with v number (see Fig. 7)[43]. The mechanism and kinetics of collisional decay of highly vibrational XeCl(B,C) excimers with buffer gases (He, Ne, Ar, Kr) is also presented (r.(27)-(30)) [43]. The relaxed XeCl(B,C) excimers decay also in the two-and three-body quenching with Xe and RCl molecules. The mechanism and kinetics of above processes is shown (see reaction (35)-(37) and Tab. 4).

2

Kinetic intermediates of unfolding of dimeric prostatic phosphatase

94%

Kuciel R. , Mazurkiewicz A. , Dudzik P.

Acta Biochimica Polonica

|

2007

|

tom 54

|

nr 2

371-377

EN

Kinetics of guanidine hydrochloride (GdnHCl)-induced unfolding of human prostatic acid phosphatase (hPAP), a homodimer of 50 kDa subunit molecular mass was investigated with enzyme activity measurements, capacity for binding an external hydrophobic probe, 1-anilinonaphtalene-8-sulfonate (ANS), accessibility of thiols to reaction with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and 2-(4'-maleimidylanilino)naphthalene-6-sulfonate (MIANS) and ability to bind Congo red dye. Kinetic analysis was performed to describe a possible mechanism of hPAP unfolding and dissociation that leads to generation of an inactive monomeric intermediate that resembles, in solution of 1.25 M GdnHCl pH 7.5, at 20°C, in equilibrium, a molten globule state. The reaction of hPAP inactivation in 1.25 M GdnHCl followed first order kinetics with the reaction rate constant 0.0715 ± 0.0024 min-1 . The rate constants of similar range were found for the pseudo-first-order reactions of ANS and Congo red binding: 0.0366 ± 0.0018 min-1 and 0.0409 ± 0.0052 min-1, respectively. Free thiol groups, inaccessible in the native protein, were gradually becoming, with the progress of unfolding, exposed for the reactions with DTNB and MIANS, with the pseudo-first-order reaction rate constants 0.327 ± 0.014 min-1 and 0.216 ± 0.010 min-1, respectively. The data indicated that in the course of hPAP denaturation exposure of thiol groups to reagents took place faster than the enzyme inactivation and exposure of the protein hydrophobic surface. This suggested the existence of a catalytically active, partially unfolded, but probably dimeric kinetic intermediate in the process of hPAP unfolding. On the other hand, the protein inactivation was accompanied by exposure of a hydrophobic, ANS-binding surface, and with an increased capacity to bind Congo red. Together with previous studies these results suggest that the stability of the catalytically active conformation of the enzyme depends mainly on the dimeric structure of the native hPAP.

3

Density functional studies of the cobaltous acid dimer : preliminary results

84%

Gajewski G. , Latajka Z. , Ratajczak H.

Bulletin of the Polish Academy of Sciences. Chemistry

|

2002

|

tom Vol. 50, No. 2

131-137

EN

The structure, interaction energy and vibrational frequencies of the hydrogen bonded cobaltous acid monomer and dimer were investigated at the B3LYP level with the CEP-31G** basis set. The cobaltous acid forms stable cyclic dimer with the dimerization energy of about -14 kcal/mol. The structural parameters of monomers are strongly perturbed upon dimerization, and the vibrational spectra are predicted to show large vibrational shifts compared with the monomer spectra.

4

Nowe formy lizozymu możliwości produkcji i wykorzystania

84%

Leśnierowski G. , Cegielska-Radziejewska R.

Przemysł Spożywczy

|

2016

|

tom T. 70, nr 4

27--29

PL

Lizozym to białko enzymatyczne, powszechnie występujące w przyrodzie, charakteryzujące się wieloma użytecznymi właściwościami, które umożliwiają wszechstronne jego wykorzystanie. Obecnie praktyczne zastosowanie enzymu dotyczy monomeru, a już wkrótce zapewne także jego zmodyfikowanej postaci. W porównaniu z monomerem zmodyfikowany lizozym wykazuje bowiem zdecydowanie większe możliwości przeciwdrobnoustrojowego działania. Dzieje się tak dzięki pojawieniu się w nim nowej, specyficznej, antybakteryjnej aktywności wobec drobnoustrojów Gram-ujemnych. Wykazuje wiele nowych właściwości, istotnych z punktu widzenia medycznego, farmaceutycznego i weterynaryjnego. Można się zatem spodziewać, że zmodyfikowany enzym będzie praktycznie wykorzystywany nie tylko w przemyśle spożywczym, ale także w medycynie, weterynarii i farmakologii. Obecnie prowadzone badania pozwoliły na opracowanie oryginalnych sposobów modyfikacji lizozymu, umożliwiających wytworzenie produktu wysokiej jakości. Niektóre z tych metod, np. metodę termiczną, termiczno-chemiczną, chemiczną czy membranową, w prosty sposób można przenieść z warunków laboratoryjnych do skali półtechnicznej czy nawet przemysłowej.

EN

Lysozyme is an enzyme protein, commonly found in nature, characterized by many useful properties that allow its versatile use. The current practical application of the enzyme concerns monomer, and soon, also its modified forms. Wider use should be linked just with the possibility of using the modified enzyme and not only in the food industry but also in medicine, veterinary medicine and pharmacology. Current research allowed developing original methods to modify lysozyme, enabling manufacture of a high quality product. Some of them, like thermal, thermalwidzenia -chemical, and chemical or membrane method are easy to be transferred from the laboratory conditions to the pilot or even industrial scale. The aim of this study was to present the methods of obtaining and modifying lysozyme causing its oligomerization, the methods of assessment of physicochemical properties of the modified lysozyme and its antibacterial action and the possibility of its practical application.

5

Association of model peptides and dehydropeptides: N-acetyl-l-butyrine and (Z)-dehydrobutyrine N',N'-dimethylamides

83%

Broda M. A. , Rzeszotarska B.

Acta Biochimica Polonica

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2006

|

tom 53

|

nr 1

221-226

EN

These comparative studies on the aggregation behaviour of Ac-(Z)-ΔAbu-NMe2 and Ac-L-Abu-NMe2 in carbon tetrachloride were performed by the analysis of their FTIR spectra and by theoretical calculations. The percentage of the monomeric form (α) decreased as concentration increased and this occurred to a higher degree for the (Z)-ΔAbu derivative than for its saturated analogue. The dimerization constant KD, calculated on the basis of the intensity of the monomer and associate bands in the νs(N-H) vibration region, is by three orders of magnitude larger for Ac-(Z)-ΔAbu-NMe2 than for Ac-L-Abu-NMe2. The obtained dimer geometries of the dehydro- compound were calculated by the B3LYP/6-31+G** method.

6

Crystal Structure, Infrared Spectra and Density Functional Theory Study on 2,3-Diketo-benzopiperazine Dimer

83%

Zhao P. , Jian F. F. , Xiao H. , Sun P.

Polish Journal of Chemistry

|

2004

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tom Vol. 78 / nr 10

1935-1944

EN

2,3-Diketo-benzopiperazine, which exists as dimeric form in its crystal structure has been synthesized. The calculated results on the dimer at B3LYP/6-31G* level show that the average strength of the double hydrogen bonds is of medium-grade. Natural bond orbital analyses have been performed. The predicted harmonic vibration frequencies support the experimental values. The thermodynamic properties of the dimer at different temperatures have been calculated and the change of Gibbs free energy for the aggregation from the monomer to the dimerDelta GT = -30.86 kJ/mol at 298.15 K, which implies the spontaneous process of the dimer formation.

7

Isoelectronic dimers [(XH3)2, (YH2)2, (ZH)2, and (Rg)2] in the groups of the periodic system: ab initio quantum chemical calculations

71%

Hobza P. , Burda J. V. , Zahradnik R.

Polish Journal of Chemistry

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1998

|

tom Vol. 72, nr 7S

1497-1504

EN

The (ZH)2, (YH2)2, (XH3)2 and (Rg)2 dimers [Z=F-At; Y=O.Po; X=N, Bi; Rg=rare gas] were studied ab initio using the CCSD(T) and MP2 procedures. Average relativistic effective potentials were used for all the halogens, while Stuttgart effective core potentials were used for the remaining non-hydrogen atoms. All the (HX)2 structure are H-bonded. All the stabilization energies mutually approach when passing down the group of the periodic system.

8

Heat and SDS insensitive NDK dimers are largely stabilised by hydrophobic interaction to form functional hexamer in Mycobacterium smegmatis

71%

Arumugam M. , Ajitkumar P.

Acta Biochimica Polonica

|

2013

|

tom 60

|

nr 2

EN

The primary structure and function of nucleoside diphosphate kinase (NDK), a substrate non-specific enzyme involved in the maintenance of nucleotide pools is also implicated to play pivotal roles in many other cellular processes. NDK is conserved from bacteria to human and forms a homotetramer or hexamer to exhibit its biological activity. However, the nature of the functional oligomeric form of the enzyme differs among different organisms. The functional form of NDKs from many bacterial systems, including that of the human pathogen, Mycobacterium tuberculosis (MtuNDK), is a hexamer, although some bacterial NDKs are tetrameric in nature. The present study addresses the oligomeric property of MsmNDK and how a dimer, the basic subunit of a functional hexamer, is stabilized by hydrogen bonds and hydrophobic interactions. Homology modeling was generated using the three-dimensional structure of MtuNDK as a template; the residues interacting at the monomer-monomer interface of MsmNDK were mapped. Using recombinant enzymes of wild type, catalytically inactive mutant, and monomer-monomer interactive mutants of MsmNDK, the stability of the dimer was verified under heat, SDS, low pH, and methanol. The predicted residues (Gln17, Ser24 and Glu27) were engaged in dimer formation, however the mutated proteins retained the ATPase and GTPase activity even after introducing single (MsmNDK- Q17A, MsmNDK-E27A, and MsmNDK-E27Q) and double (MsmNDK-E27A/Q17A) mutation. However, the monomer-monomer interaction could be abolished using methanol, indicating the stabilization of the monomer-monomer interaction by hydrophobic interaction.

9

Changes of quantities of tocopherols and their dimers during storage of soya-bean oil under N2 and under air

71%

Gogolewski M. , Galuba G. , Bartkowiak-Fludra E. , Jasinska-Stepniak A.

Food Science and Technology. Scientific Papers of Agricultural University of Poznan

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2000

|

tom 04

10

Crystal structure of the alpha-actinin rod: four spectrin repeats forming a tight dimer

71%

Ylanne J. , Scheffzek K. , Young P. , Saraste M.

Cellular and Molecular Biology Letters

|

2001

|

tom 06

|

nr 2

11

Conformational analysis of 1,2,4,5-tetroxane

67%

Jorge N. , Gomez-Vara M. , Romero J. R. , Castro E. A.

Bulletin of the Polish Academy of Sciences. Chemistry

|

2002

|

tom Vol. 50, No. 3

387-395

EN

Different theoretical procedures are applied to make a conformational study of the 1,2,4,5-tetroxane molecule: AMI semi-empirical method, ab initio RHF method at the 3-21+G and 6-311+G(d,p) basis set levels and B3LYP density functional method at the same basis set levels. The molecular stability is analyzed on the basis of different stereo-electronic and symmetry features. There is a general agreement between these methods and all of them predict the chair conformation to be the most stable conformer.

12

Mutational analysis of the AtNUDT7 Nudix hydrolase from Arabidopsis thaliana reveals residues required for protein quarternary structure formation and activity

59%

Olejnik K. , Plochocka D. , Grynberg M. , Goch G. , Gruszecki W. I. , Basinska T. , Kraszewska E.

Acta Biochimica Polonica

|

2009

|

tom 56

|

nr 2

291-300

EN

Arabidopsis thaliana AtNUDT7, a homodimeric Nudix hydrolase active on ADP-ribose and NADH, exerts negative control on the major signaling complex involved in plant defense activation and programmed cell death. The structural and functional consequences of altering several amino-acid residues of the AtNUDT7 protein have been examined by site-directed mutagenesis, far-UV circular dichroism (CD), attenuated total reflection-Fourier transform infrared (ATR-FTIR) and photon correlation (PCS) spectroscopy, biochemical analysis and protein-protein interaction studies. Alanine substitutions of F73 and V168 disallowed dimer formation. Both the F73A- and V168A-mutated proteins displayed no observable enzymatic activity. Alanine substitution of the V69 residue did not significantly alter the enzyme activity and had no influence on dimer arrangement. The non-conserved V26 residue, used as a negative control, did not contribute to the enzyme quaternary structure or activity. Detailed biophysical characterization of the wild-type and mutant proteins indicates that the mutations do not considerably alter the secondary structure of the enzyme but they affect dimer assembly. In addition, mutating residues V69, F73 and V168 disrupted the binding of AtNUDT7 to the regulatory 14.3.3 protein. These are the first studies of the structure-function relationship of AtNUDT7, a Nudix hydrolase of important regulatory function.

13

Heat and SDS insensitive NDK dimers are largely stabilised by hydrophobic interaction to form functional hexamer in Mycobacterium smegmatis

59%

Arumugam M. , Ajitkumar P.

Acta Biochimica Polonica

|

2013

|

tom 60

|

nr 2

199-207

EN

The primary structure and function of nucleoside diphosphate kinase (NDK), a substrate non-specific enzyme involved in the maintenance of nucleotide pools is also implicated to play pivotal roles in many other cellular processes. NDK is conserved from bacteria to human and forms a homotetramer or hexamer to exhibit its biological activity. However, the nature of the functional oligomeric form of the enzyme differs among different organisms. The functional form of NDKs from many bacterial systems, including that of the human pathogen, Mycobacterium tuberculosis (MtuNDK), is a hexamer, although some bacterial NDKs are tetrameric in nature. The present study addresses the oligomeric property of MsmNDK and how a dimer, the basic subunit of a functional hexamer, is stabilized by hydrogen bonds and hydrophobic interactions. Homology modeling was generated using the three-dimensional structure of MtuNDK as a template; the residues interacting at the monomer-monomer interface of MsmNDK were mapped. Using recombinant enzymes of wild type, catalytically inactive mutant, and monomer-monomer interactive mutants of MsmNDK, the stability of the dimer was verified under heat, SDS, low pH, and methanol. The predicted residues (Gln17, Ser24 and Glu27) were engaged in dimer formation, however the mutated proteins retained the ATPase and GTPase activity even after introducing single (MsmNDK- Q17A, MsmNDK-E27A, and MsmNDK-E27Q) and double (MsmNDK-E27A/Q17A) mutation. However, the monomer-monomer interaction could be abolished using methanol, indicating the stabilization of the monomer-monomer interaction by hydrophobic interaction.

14

Synteza dimerów i estolidów nienasyconych kwasów tłuszczowych oraz ich adduktów z bezwodnikiem maleinowym

59%

Wasilewicz-Niedbalska W. , Chmielarz B. , Kosmacińska B. , Dyczewski M. , Wiślicki B. , Zdrodowska B.

Przemysł Chemiczny

|

2001

|

tom T. 80, nr 2

52-55

15

Mutational analysis of the AtNUDT7 Nudix hydrolase from Arabidopsis thaliana reveals residues required for protein quarternary structure formation and activity

59%

Olejnik K. , Płochocka D. , Grynberg M. , Goch G. , Gruszecki W. I. , Basińska T. , Kraszewska E.

Acta Biochimica Polonica

|

2009

|

tom 56

|

nr 2

291-300

EN

Arabidopsis thaliana AtNUDT7, a homodimeric Nudix hydrolase active on ADP-ribose and NADH, exerts negative control on the major signaling complex involved in plant defense activation and programmed cell death. The structural and functional consequences of altering several amino-acid residues of the AtNUDT7 protein have been examined by site-directed mutagenesis, far-UV circular dichroism (CD), attenuated total reflection-Fourier transform infrared (ATR-FTIR) and photon correlation (PCS) spectroscopy, biochemical analysis and protein-protein interaction studies. Alanine substitutions of F73 and V168 disallowed dimer formation. Both the F73A- and V168A-mutated proteins displayed no observable enzymatic activity. Alanine substitution of the V69 residue did not significantly alter the enzyme activity and had no influence on dimer arrangement. The non-conserved V26 residue, used as a negative control, did not contribute to the enzyme quaternary structure or activity. Detailed biophysical characterization of the wild-type and mutant proteins indicates that the mutations do not considerably alter the secondary structure of the enzyme but they affect dimer assembly. In addition, mutating residues V69, F73 and V168 disrupted the binding of AtNUDT7 to the regulatory 14.3.3 protein. These are the first studies of the structure-function relationship of AtNUDT7, a Nudix hydrolase of important regulatory function.

16

Preparation of alpha-, gamma-, delta-tocopherol dimers and their analysis with HPLC

59%

Galuba G. A. , Gogolewski M. , Jasinska-Stepniak A.

Food Science and Technology. Scientific Papers of Agricultural University of Poznan

|

1998

|

tom 02

17

Overproduction and purification of the CepA protein from Lactococcus lactis

59%

Kowalczyk M. , Bardowski J.

Acta Biochimica Polonica

|

2003

|

tom 50

|

nr 2

EN

In this work we present cloning and overexpression of lactococcal CcpA protein in Escherichia coli Xllblue strain as a fusion with 6xHis tag. A high yield of the CcpA protein was obtained when the cells were cultured in liquid medium LB with 100 ug/ml ampicillin at 37°C and subsequently for 4 h after induction by IPTG. The procedure let us obtain 5 mg of homogenous CcpA protein. Glutaraldehyde crosslinking analysis indicated the formation of dimer or tetramer forms of the CcpA protein.

18

Kinetic intermediates of unfolding of dimeric prostatic phosphatase

59%

Kuciel R. , Mazurkiewicz A. , Dudzik P.

Acta Biochimica Polonica

|

2007

|

tom 54

|

nr 2

EN

Kinetics of guanidine hydrochloride (GdnHCl)-induced unfolding of human prostatic acid phosphatase (hPAP), a homodimer of 50 kDa subunit molecular mass was investigated with enzyme activity measurements, capacity for binding an external hydrophobic probe, 1-anilinonaphtalene-8-sulfonate (ANS), accessibility of thiols to reaction with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and 2-(4'-maleimidylanilino)naphthalene-6-sulfonate (MIANS) and ability to bind Congo red dye. Kinetic analysis was performed to describe a possible mechanism of hPAP unfolding and dissociation that leads to generation of an inactive monomeric intermediate that resembles, in solution of 1.25 M GdnHCl pH 7.5, at 20°C, in equilibrium, a molten globule state. The reaction of hPAP inactivation in 1.25 M GdnHCl followed first order kinetics with the reaction rate constant 0.0715 ± 0.0024 min-1. The rate constants of similar range were found for the pseudo-first-order reactions of ANS and Congo red binding: 0.0366 ± 0.0018 min-1 and 0.0409 ± 0.0052 min-1, respectively. Free thiol groups, inaccessible in the native protein, were gradually becoming, with the progress of unfolding, exposed for the reactions with DTNB and MIANS, with the pseudo-first-order reaction rate constants 0.327 ± 0.014 min-1 and 0.216 ± 0.010 min-1, respectively. The data indicated that in the course of hPAP denaturation exposure of thiol groups to reagents took place faster than the enzyme inactivation and exposure of the protein hydrophobic surface. This suggested the existence of a catalytically active, partially unfolded, but probably dimeric kinetic intermediate in the process of hPAP unfolding. On the other hand, the protein inactivation was accompanied by exposure of a hydrophobic, ANS-binding surface, and with an increased capacity to bind Congo red. Together with previous studies these results suggest that the stability of the catalytically active conformation of the enzyme depends mainly on the dimeric structure of the native hPAP.