Complex K3 Research Articles

Kuga-Satake abelian varieties of K3 surfaces in mixed characteristic

Kuga and Satake associate with every polarized complex K3 surface (X, ℒ) a complex abelian variety called the Kuga-Satake abelian variety of (X, ℒ). We use this construction to define morphisms between moduli spaces of polarized K3 surfaces with certain level structures and moduli spaces of polarized abelian varieties with level structure over ℂ. In this note we study these morphisms. We prove first that they are defined over finite extensions of ℚ. This is done by proving analogues of the main theorems of complex multiplication for abelian varieties for K3 surfaces. Then we show that they extend in positive characteristic. In this way we give an indirect construction of Kuga-Satake abelian varieties over an arbitrary base. We also give some applications of this construction to canonical lifts of ordinary K3 surfaces.

The Chow Motive of a K3 Surface

In this note we present some results on the Chow motive h(X) of an algebraic surface X and relate them to the conjectures of Bloch, Beilinson and Murre. In particular we illustrate the relations between the finite-dimensionality of h(X) and the geometric properties of the surface. Then we focus on the case, where the conjectures are still open, of a complex K3 surface and prove some results which give some evidence to the finite-dimensionality of h(X).

K3 surfaces with non-symplectic automorphisms of 2-power order

This paper concerns complex algebraic K3 surfaces with an automorphism which acts trivially on the Néron–Severi group. Complementing a result by Vorontsov and Kondō, we determine those K3 surfaces where the order of the automorphism is a 2-power and equals the rank of the transcendental lattice. We also study the arithmetic of these K3 surfaces and comment on relations with mirror symmetry.

Gluing construction of compact complex surfaces with trivial canonical bundle

We obtain a new construction of compact complex surfaces with trivial canonical bundle. In our construction we glue together two compact complex surfaces with an anticanonical divisor under suitable conditions. Then we show that the resulting compact manifold admits a complex structure with trivial canonical bundle by solving an elliptic partial differential equation. We generalize this result to cases where we have other than two components to glue together. With this generalization, we construct examples of complex tori, Kodaira surfaces and K3 surfaces. Lastly we deal with the smoothing problem of a normal crossing complex surface X with at most double curves. We prove that we still have a family of smoothings of X in a weak sense even when X is not Kahlerian or H 1 ( X , O X ) ≠ 0 , in which cases the smoothability result of Friedman [Fr] is not applicable.

Finite groups of symplectic automorphisms of K3 surfaces in positive characteristic

We show that Mukai's classification of finite groups which may act symplectically on a complex K3 surface extends to positive characteristic p under assumptions that (i) the order of the group is coprime to p and (ii) either the surface or its quotient is not birationally isomorphic to a supersingular K3 surface with Artin invariant 1. In the case without assumption (ii) we classify all possible new groups which may appear. We prove that assumption (i) on the order of the group is always satisfied if p > 11. For p = 2,3,5,11, we give examples of K3 surfaces with finite symplectic automorphism groups of order divisible by p which are not contained in Mukai's list.

Stability conditions on K3 surfaces

This article contains a description of one connected component of the space of stability conditions on the bounded derived category of coherent sheaves on a complex algebraic K3 surface

Transient State Kinetic Studies of the MutT-Catalyzed Nucleoside Triphosphate Pyrophosphohydrolase Reaction

The MutT pyrophosphohydrolase, in the presence of Mg2+, catalyzes the hydrolysis of nucleoside triphosphates by nucleophilic substitution at Pbeta, to yield the nucleotide and PP(i). The best substrate for MutT is the mutagenic 8-oxo-dGTP, on the basis of its Km being 540-fold lower than that of dGTP. Product inhibition studies have led to a proposed uni-bi-iso kinetic mechanism, in which PP(i) dissociates first from the enzyme-product complex (k3), followed by NMP (k4), leaving a product-binding form of the enzyme (F) which converts to the substrate-binding form (E) in a partially rate-limiting step (k5) [Saraswat, V., et al. (2002) Biochemistry 41, 15566-15577]. Single- and multiple-turnover kinetic studies of the hydrolysis of dGTP and 8-oxo-dGTP and global fitting of the data to this mechanism have yielded all of the nine rate constants. Consistent with an "iso" mechanism, single-turnover studies with dGTP and 8-oxo-dGTP hydrolysis showed slow apparent second-order rate constants for substrate binding similar to their kcat/Km values, but well below the diffusion limit (approximately 10(9) M(-1) s(-1)): k(on)app = 7.2 x 10(4) M(-1) s(-1) for dGTP and k(on)app = 2.8 x 10(7) M(-1) s(-1) for 8-oxo-dGTP. These low k(on)app values are fitted by assuming a slow iso step (k5 = 12.1 s(-1)) followed by fast rate constants for substrate binding: k1 = 1.9 x 10(6) M(-1) s(-1) for dGTP and k1 = 0.75 x 10(9) M(-1) s(-1) for 8-oxo-dGTP (the latter near the diffusion limit). With dGTP as the substrate, replacing Mg2+ with Mn2+ does not change k1, consistent with the formation of a second-sphere MutT-M2+-(H2O)-dGTP complex, but slows the iso step (k5) 5.8-fold, and its reverse (k(-5)) 25-fold, suggesting that the iso step involves a change in metal coordination, likely the dissociation of Glu-53 from the enzyme-bound metal so that it can function as the general base. Multiple-turnover studies with dGTP and 8-oxo-dGTP show bursts of product formation, indicating partially rate-limiting steps following the chemical step (k2). With dGTP, the slow steps are the chemical step (k2 = 10.7 s(-1)) and the iso step (k5 = 12.1 s(-1)). With 8-oxo-dGTP, the slow steps are the release of the 8-oxo-dGMP product (k4 = 3.9 s(-1)) and the iso step (k5 = 12.1 s(-1)), while the chemical step is fast (k2 = 32.3 s(-1)). The transient kinetic studies are generally consistent with the steady state kcat and Km values. Comparison of rate constants and free energy diagrams indicate that 8-oxo-dGTP, at low concentrations, is a better substrate than dGTP because it binds to MutT 395-fold faster, dissociates 46-fold slower, and has a 3.0-fold faster chemical step. The true dissociation constants (KD) of the substrates from the E-form of MutT, which can now be obtained from k(-1)/k1, are 3.5 nM for 8-oxo-dGTP and 62 microM for dGTP, indicating that 8-oxo-dGTP binds 1.8 x 10(4)-fold tighter than dGTP, corresponding to a 5.8 kcal/mol lower free energy of binding.

K3 surfaces via almost-primes

Based on the result on derived categories on K3 surfaces due to Mukai and Orlov and the result concerning almost-prime numbers due to Iwaniec, we remark the following fact: For any given positive integer N, there are N (mutually non-isomorphic) projective complex K3 surfaces such that their Picard lattices are not isomorphic but their transcendental lattices are Hodge isometric, or equivalently, their derived categories are mutually equivalent. After reviewing some finiteness result, we also give an explicit formula for the cardinality of the isomorphism classes of projective K3 surfaces having derived categories equivalent to the one of X with Picard number 1 in terms of the degree of X.

On the Thermal Decompositions of the Trivalent Trioxalato Complexes of Al, Cr, Mn, Fe and Co

The thermal decompositions of the complexes K3[M(ox)3]⋅3H2O(M=Al, Cr, Mn, Fe, Co; ox=C2O42−) were studied. Dehydration of the complexes occurs up to 200°C, this being a three-step process for M=Al, Cr, Mn and Co, and a two-step process for M=Fe. Decomposition of the dehydrated complexes proceeds in several steps. For M=Al, Cr and Fe, the decomposition takes place with the evolution of CO, whereas for M=Mn and Co the decomposition of the oxalate ligand yields solid C besides CO. The temperature of CO liberation decreases in the series Cr<Al<Co<Mn<Fe. For M=transition metal, this trend can be explained by the fact that the strength of the C—C bond in the oxalate ligand decreases in the series Cr<Co<Mn<Fe.

One-Bond55Mn,13C Coupling Constants, a Correction

Previously published one-bond 55Mn,13C coupling constants have been recalculated using a revised lineshape fitting program, QUADR. The accuracy of the new data was confirmed by the simulation of quadrupole-broadened but resolved 13C and 19F spectra of the model complexes K3[Co(CN)6] and Li[AsF6]. The 55Mn,13C coupling constants lie in the range 128–189 Hz for Mn—CO bonds, 57–114 Hz for Mn—C(sp2) bonds and 35–79 Hz for Mn—C(sp3) bonds.

Thermodynamic Investigation of Atomic Order in Molten K-Bi Alloys

Abstract The assymmetry observed in the concentration dependence of the thermodynamic properties of K-Bi is investigated using an empirical model which assumes a process of heterocoordination. The model is further used to explain the concentration dependence of some thermodynamic properties viz.: free energy of mixing, heat of mixing and the excess entropy of mixing. Our calculations in most cases yield qualitative agreement with experiment for all quantities investigated and are also used to supplement experimental data. We conclude by stating that the formation of the complex K3 Bi is of a weak nature in the liquid phase. Compound formation persists at all concentrations but the K-rich end of the phase diagram is more ordered.

Gallium(III) Catecholate Complexes as Probes for the Kinetics and Mechanism of Inversion and Isomerization of Siderophore Complexes1

The catechol siderophore analog K3[Ga(3)3], 4 (H23 = 2,3-dihydroxy-N,N‘-diisopropylterephthalamide), is D3-symmetric in aqueous solution, and exists in two enantiomeric forms, Δ-4 and Λ-4. Variable temperature NMR experiments demonstrate that the inversion of the enantiomers of 4 in D2O is facile. The rate of inversion is independent of pH above pH 8. The mechanism is intramolecular. From line-shape analysis the free energy of activation ΔG⧧298 = 67.4(9) kJ mol-1 in D2O at pD 12.1, with ΔH⧧ = 58.5(6) kJ mol-1 and ΔS⧧ = −0.030(9) kJ mol-1 K-1. Below pD 8 the rate of inversion for 4 is pD dependent and initially first order in [D+]. Potentiometric titrations reveal that 4 protonates in two one-proton steps with log KHML3 = 4.66(4) and log KH2ML3 = 3.99(7). In DMSO-d6, formation of a tight contact ion pair between K+ and [Ga(3)3]3- ions increases the free energy barrier to inversion by ∼7 kJ mol-1. The complex K3[Ga(9)3], 10 (H29 = 2,3-dihydroxy-N-tert-butyl-N‘-benzylterephthalamide), was prepared to elucida...

Kinetic studies on the inhibition of isopeptidase T by ubiquitin aldehyde.

Isopeptidase T (IPaseT) can hydrolyze isopeptide bonds of polyubiquitin (polyUb) chains, simple C-terminal derivatives of Ub, and certain peptides. We recently reported that IPaseT is regulated by ubiquitin (Ub); while submicromolar Ub activates, higher concentrations inhibit this enzyme [Stein et al. (1995) Biochemistry 34, 12616]. To explain these observations, we proposed a model for IPaseT involving two binding sites for Ub. According to the model, the two sites are adjacent to one another and are the extended active site that binds two Ub moieties of a polyUb chain. The "activation site" binds the Ub that donates Lys to the isopeptide bond. The "inhibition site" is adjacent and binds the Ub that donates the C-terminal Gly to the isopeptide bond. We now report that the interaction of IPaseT with the C-terminal aldehyde of Ub (Ub-H) is also modulated by Ub. In the absence of Ub, Ub-H inhibits IPaseT with a Ki of 2.3 nM, while at 0.6 microM Ub, where the "activation site" is occupied, Ki is less than 0.1 nM. At high Ub concentrations, where both the "activation" and "inhibition" sites are occupied, IPaseT cannot bind Ub-H. We also determined the kinetics of inhibition of IPaseT by Ub-H. In the absence of Ub, a two-step mechanism is followed. In the first step, Ub-H slowly combines with IPaseT to form a relatively weak complex (K1 = 260 nM) that slowly isomerizes to the final, stable complex that accumulates in the steady-state (k2 = 2 x 10(-3) s-1; k-2 = 0.02 x 10(-3) s-1). In contrast, Ub-activated IPaseT is inhibited by Ub-H through a three-step process. In the first step, Ub-H rapidly combines with IPaseT to form a complex (K1 = 10 nM) that slowly isomerizes to a second, more stable complex (k2 = 18 x 10(-3) s-1; k-2 = 1.5 x 10(-3) s-1). In the third step, the second complex converts to the final complex (k3 = 1.5 x 10(-3) s-1; k-3 < 0.2 x 10(-3) s-1). To unify the results of this study with our previous results on catalysis, we propose that binding of Ub either to catalytic transition states or to tetrahedral inhibition intermediates liberates more free energy than binding of Ub to the reactant state of IPaseT and that IPaseT can utilize this binding energy to stabilize both of these tetrahedral species. The overall effect is a Ub-induced increase in catalytic efficiency or inhibitory potency.

Kinetic mechanism of the DNA-dependent DNA polymerase activity of human immunodeficiency virus reverse transcriptase.

The kinetic pathway of DNA-dependent DNA polymerase activity of human immunodeficiency virus reverse transcriptase (HIV RT) as determined by pre-steady-state methods using a defined primer/template is as follows, [formula: see text] where E is RT, Dn,n+1 is primer/template, dNTP is deoxyribonucleoside triphosphate, and PPi is pyrophosphate. The rate-determining step for enzyme turnover in single nucleotide addition is the dissociation of enzyme from DNA (k6 = 0.11 s-1). The observation of an E'.DNA.dNTP intermediate by pulse-chase analysis and the absence of a phosphorothioate elemental effect identified the rate-limiting step for nucleotide addition as a conformational change of the E.DNA.dNTP complex (k3 = 83 s-1) prior to the chemical step. Biphasic kinetics of single-turnover pyrophosphorolysis suggested that this conformational change (k-3 = 0.3 s-1) is also rate-limiting for the reverse reaction. The equilibrium constant for the chemical step (K4) is 3.8, in slight favor of the forward reaction. The large equilibrium constant (K3 = 280) for the conformational change effectively renders nucleotide addition kinetically irreversible. The dissociation constant for primer/template is 26 nM, and the association rate of enzyme and DNA (k1) is 2.3 x 10(6) M-1 s-1. Equilibrium dissociation constants for dTTP and PPi are 18 microM and 7.2 mM, respectively. Mg2+ enhances productive interaction of RT with DNA as judged by a 50% increase in burst amplitude in the single nucleotide addition reaction and by an 8-fold decrease in KD for the RT.DNA complex as determined by gel mobility shift assay. Secondary interactions of the RT.DNA complex with free DNA were observed in the absence of Mg2+.

Synthesis and characterization of iron(III) and iron(IV) complexes of N-(2-hydroxyphenyl)salicylamide and homologs

The complexation of tridentate trianionic chelating ligands, N-(2-hydroxyphenyl)salicylamide (H3L1) and its homologs with a substituent on the 2-hydroxyphenyl moiety (5-CH3, H3L2; 5-Cl, H3L3), toward iron ion has been studied. The ligand H3L1 formed a high-spin iron(III) complex K3[Fe(L1)2] when treated with FeCl3 in an alkaline solution under open atmosphere. This complex was oxidized with Ce(IV) to a high-spin iron(IV) complex (NPr4)2[Fe(L1)2]. The ligand H3L2 formed a low-spin iron(IV) complex K2[Fe(L2)2] under open atmosphere, whereas the ligand H3L3 gave a high-spin iron(III) complex (PBu4)3[Fe(L3)2]. The complexes were characterized by means of cyclic voltammetry, electronic spectra and Mössbauer spectra.

Kinetics of the formation and decomposition of complexes of chlorine atoms and aromatic solvents

1. The absorption spectra were recorded, and the constants and heats of formation of complexes of atomic chlorine with four aromatic solvents were determined. 2. The rate constants and enthalpies of activation of bimolecular reactions of decomposition of the complexes 2k2 and k3 were determined. Decomposition of the complexes is limited by diffusion. 3. The rate constants for formation and dissociation of the complexes and recombination of chlorine atoms were calculated on the assumption of diffusion control. 4. Introduction of oxygen in the air into the solutions results in acceleration of the decomposition of the complexes due to the reaction of the complexes and/or the chlorine atoms with the oxygen.

The chloro and bromo complexes of iridium(III) and iridium(IV). II. Structural chemistry of IrIII complexes

The single-crystal X-ray structures of the tervalent iridium complexes K3 [IrCl6] [P1, a 1263.1, b 7029, c 702.7 pm, Ir-Cl(mean) 236.8 pm], K3 [IrCl6].H2O [C1 (1), a 1243.6, b 1568.2, c 1207.2 pm, Ir-Cl (mean) 236.8 pm], (NH4)3 [IrCl6].H2O [Cs(m), a 1222.9, b 701.1 c, 1408.8 pm, Ir-Cl (mean) 236.7 pm] and Rb3 [IrBr,].H2O [Pnma, a 1276.8, b 739.1, c 1498.2pm, Ir-Br(mean) 250.8 pm] have been determined. From preliminary single-crystal studies, and X-ray powder diffraction, the structures of a number of other hexachloro and hexabromo complexes of IrIII have been determined. In all cases the halogeno anions are distorted as a consequence of the non-spherical packing of the cations and in some cases water molecule around the anions.

ChemInform Abstract: RESONANCE‐RAMAN STUDIES OF THE NITRIDE‐BRIDGED COMPLEX K3(RU2NCL8(OH2)2)

Chemischer InformationsdienstVolume 12, Issue 30 Physical Inorganic Chemistry ChemInform Abstract: RESONANCE-RAMAN STUDIES OF THE NITRIDE-BRIDGED COMPLEX K3(RU2NCL8(OH2)2) J. R. CAMPBELL, J. R. CAMPBELLSearch for more papers by this authorR. J. H. CLARK, R. J. H. CLARKSearch for more papers by this author J. R. CAMPBELL, J. R. CAMPBELLSearch for more papers by this authorR. J. H. CLARK, R. J. H. CLARKSearch for more papers by this author First published: July 28, 1981 https://doi.org/10.1002/chin.198130017AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue30July 28, 1981 RelatedInformation

Photosensitized electron transport across a liquid membrane containing photosensitizer, electron mediator, and carrier

Photosensitized electron transport from ethylenediaminetetra-acetic acid or Fe2+ to Fe(CN)63– proceeded across a liquid membrane containing both a surface active ruthenium(II) complex and vitamin K3, supported on a millipore filter; the incorporation of an electron mediator comprising a surface-active nicotinamide chloride of 4,4′-bipyridylium dichloride into the membrane system brought about a marked enhancement in the rate of electron transport.

Resonance-Raman studies of the nitride-bridged complex K3[Ru2NCl8(OH2)2

The resonance-Raman spectrum of K3[Ru2NCl8(OH2)2], along with Raman-band excitation-profile measurements, indicates that the electronic band at 31 200 cm–1 of the complex in the solid state may be assigned to the eu*â†�eg,1A2uâ†�1A1g transition of the π-bond system of the linear Ru–N–Ru bridge.