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Based an identity-based signature scheme, we givea certificateless signature scheme. And then we propose a certificateless blind signature (CLBS) scheme in this paper. This schemeis more efficient than those of previous schemes by pre-computing the pairing e (P, P)=g. Based on CL-PKC, it eliminates theusing of certificates in the signature scheme with respect to thetraditional public key cryptography (PKC) and solves key escrowproblems in ID-based signature schemes. Meanwhile it retains themerits of BS schemes. The proposed CLBS scheme is existentialunforgeable in the random oracle model under the intractabilityof the q-Strong Diffie-Hellman problem.

[Me4N]10[Fe4(OH)4(PW10O37)2] 15H2O was synthesized by the reaction of FeCl3 6HzO, with A-Na8HPW9O34 and Me4NBr. Crystal data: M = 6225.75, space group P21/c with he monoclinic parameters: a = 1.3228(5), b=3.5634(3), c = 1.5226(2) nm, β = 94.20(2), V = 7.1576nm3, Z = 2,Dc = 2.888 g/cm3, Mo Ka radiation (λ = 0.071069 nm), μ = 168.534 cm−1, F(000) = 5576, final R = 0.0428 and Rw = 0.1204 for 7086 observed reflections with I 2s(I). The structure of the title compound is the first structurally characterized heteropolymetalate with hydroxo-bridging metal aggregation Fe4(OH)4 encapsulated in the dimer of Keggin polyoxoanion.

Deoxybaccatin VI (4α,7β,9α,10β,13α-penta-acetoxy-2a-benzoyloxy-5β,20-epoxytax-11-ene) was isolated from the roots of Taxus chinensis, Rehd. var mairei. The structural assignments of the compound were based on their spectral data, including 2D NMR experiments and chemical correlation. The X-ray crystallographic analysis of 1-deoxybaccatin VI provided unambiguous characterization for the structures. In the structure, the six-membered A ring exhibits boat conformation, the eight-membered B ring adopts boat-chair conformation, and the six-membered C ring exhibits a sofa conformation.

The monomer 1 derived from achiral 1-(aminoxy)cyclopropanecarboxylic acid (OAcc) and oligopeptides 2-9 consisting of a chiral alpha-aminoxy acid and an achiral alpha-aminoxy acid such as OAcc were synthesized and their structures characterized. The eight-membered-ring intramolecular hydrogen bond, namely the alpha N-O turn, was formed between adjacent residues independent of their chirality. However, the helix formation was sequence-dependent. Dipeptide 2 bearing chiral alpha-aminoxy acid (d-OAA) at the N-terminus and achiral OAcc at the C-terminus preferentially adopted a right-handed 1.8(8) helical structure, but dipeptide 3 (OAcc-d-OAA) did not. Theoretical calculation results, in good agreement with experimental ones, revealed that the biased handedness of alpha N-O turn found in OAcc residue depends on its preceding chiral residue. It was then found that the helical conformation was destroyed in the case of oligopeptides 6 and 7 [OAA-(OAcc)(n), n = 2, 3]. The crystal structure of tripeptide 8 ((i)PrCO-d-OVal-OAcc-d-OVal-NH(i)Bu) further disclosed the helical structure formed by three consecutive homochiral alpha N-O turns. This study has uncovered achiral aminoxy acid residues such as the OAcc unit as a useful building block to be incorporated into chiral aminoxy peptides to mimic chiral helix structure.

Synthesis and crystal structures of 1-deoxybaccatin VI derivatives, and the influence of C(9), C(10), and C(13) substituents of the tetracyclic moiety on molecular conformations were investigated. Comparison of conformations of 1-deoxybaccatin VI derivatives reveals subtle conformational variations in the tetracyclic ring system due to deacetylation at C(10) and C(13), and 9,10-acetonide. Additionally, C(2)-benzoyl group exhibits an unexpected conformational flexibility in 1-deoxybaccatin VI derivatives, which may be relevant to the bioactivity of taxanes.

Two novel 4-deacetyl and 2,4-deacyl 1-deoxybaccatin VI derivatives were prepared from 1-deoxybaccatin VI. Their structures were elucidated using extensive spectroscopic techniques (IR, 1HNMR, DEPT, COSY, HMQC and MS). In addition, the conformations for these compounds were obtained by X-ray diffraction methods. Comparisons to 1-deoxybaccatin VI and paclitaxel identify relative differences principally in the cyclohexenyl ring (A ring). Conformational analysis showed that removal of 4-acetyl or 2,4-diacyl moiety has a decisive influence on the conformation of the A ring.

Reactions of silicon dioxide with water molecules have been studied by matrix isolation infrared and density functional theoretical calculations. Silicon dioxides were prepared by reactions of laser ablated silicon atoms with oxygen in excess argon. When water molecules were added in the reagent gas, silicic acid H 2 SiO 3 molecules were produced spontaneously on annealing. Isotopic substitution experiments showed that the H 2 SiO 3 molecules were formed by reactions of silicon dioxide with water. The potential energy surface for silicon dioxide and water reaction was calculated. Although silicon dioxide–water complex was predicted to be stable, this complex was not observed due to low energy barrier and high exothermicity for the hydrolysis reaction.

In the title compound, C23H27NO4, the γ-lactam ring adopts an envelope conformation. An O—H⋯O hydrogen bond links the mol­ecules into a chain which runs parallel to the c axis.

The title compound, C15H14F2N2O3, was obtained in a one-pot three-component reaction from 4-(difluoro­meth­oxy)benzaldehyde, cyclo­hexane-1,3-dione and urea, with a catalytic amount of p-toluene­sulfonic acid. The 4-(difluoro­meth­oxy)phenyl ring is positioned axially, perpendicular to, and bis­ecting the six-membered heterocyclic ring. The heterocyclic ring adopts a puckered boat conformation, whereas the cyclo­hexene ring is in a half-chair conformation. The mol­ecules are linked by N—H⋯O, C—H⋯O, N—H⋯F and C—H⋯F inter­molecular hydrogen bonds.

At 293 K, a crystalline terpenoid indole alkaloid, the title compound, C21H25N2O3 +·Cl−, has been isolated from Gelsemium elegans Benth, a Chinese folk medicine plant. Structural ambiguities have been resolved by the X-ray crystallographic analysis. Intramolecular C—H...O and intermolecular C—H...Cl, C—H...O and N—H...Cl hydrogen bonds help to stabilize the structure.

In the structure of the title compound, C20H18N2O2S, the carbonyl group, the naphthyl ring system and the cyclopentyl ring are not in the plane of the pyrimidinyl ring. In the crystal structure, pairs of molecules are connected into dimers via N—H...O hydrogen bonding

The new manganese(III) complex {[HimH]+[Mn(sal)2(py)H2O]−}2 (sal = salicylate, C7H4O3; py - pyridine, C5H5n; [HimH]+ = imidazole cation, C3H5N2) has been prepared and characterized by X-ray analysis and magnetic measurements. The structure of the title complex consists of imidazole cations and two types of mononuclear MnIII complex anions of [Mn(1)(sal)2(py)(H2O)]− and [Mn(2)(sal)(py)(H2O)]−. Each manganese(III) ion display elongated octahedral geometry with water and pyridine molecules occupying axial sites. The equatorial plane is defined by four oxygen atoms from salicylates. Each MnIII complex units is linked to its neighbors above and below by pairs of OwH…O hydrogen bonds between bound water and two noncoordinating carboxylate oxygens of salicylates of the adjacent MnIII units forming an infinite chain running parallel to the crystallographic c-axis. The two types of chains are cross-linked by NH…O hydrogen bonds with imidazolium bridges. The magnetic properties of the title complex are reported and discussed.

The title compound, 2,2′-(2,4,8,10-tetra­thia­spiro­[5.5]­undec­ane-3,9-diyl­idene)­bis­(propane­di­nitrile), C13H8N4S4, has been designed and synthesized for use as a potential new organic molecular electronic material. The spiro-annulated structure has twofold symmetry and is formed by two equal push–pull ethyl­ene units, with the cyclo­alkyl­thio groups as electron donors and the cyano groups as electron acceptors. The intermolecular S⋯N non-bonded separation within a layer in the lattice is 3.296 (6) A, indicating a strong intermolecular interaction between the cyano groups and the S atoms, while the S atoms in two neighbouring mol­ecules have a shortest S⋯S contact of 3.449 (3) A. In addition, attractive C—H⋯N and C—H⋯S interactions bridge adjacent mol­ecules either within a layer or between layers. In short, these four types of intermolecular interactions combine to form an extended three-dimensional network in the lattice, resulting in a highly ordered array of molecular packing.

Disulfide-bond formation between the side chains of cysteine-cysteine pairs is often critical to the folding behavior, stability, and functionality of proteins. In this paper, we report that sulfur atoms can be introduced into the amide groups of aminoxy peptides to form a novel type of disulfide bridge, which creates a connecting loop in the peptide backbone.

The stereochemistry at C2'' and C3'' of two diastereomers of 2'',3''-dibromo-7-epi-10-deacetylcephalomannine (6 and 7), which were synthesized by reacting 7-epi-10-deacetylcephalomannine (5) with bromine, were assigned unambiguously based on crystallographic studies of 6. The X-ray crystallographic analysis shows that 6 adopts an absolute configuration of (2''S,3''R), and 7 can be assigned as (2''R,3''S) configuration. The side-chain conformation of 6 was revealed to be different with the known hydrophobic collapse and the apolar conformations, as found in solid state and in solution. However, most side-chain torsion angles of 6 were found to be very similar to those of tubulin-bound T-shaped conformation (T-Taxol). Both 6 and 7 showed strong in vitro paclitaxel-like activity.

The title compound, C20H28O6, is an eremophilanolide which was isolated from the roots of Petasites Hybridus. The mol­ecule contains three fused rings, of which two six-membered rings adopt chair conformations and are fused in a cis configuration. In the angeloyl group, the carbonyl and methyl groups display a Z configuration about the C=C bond. The crystal structure is stabilized by O—H⋯O and C—H⋯O hydrogen bonding.

The title compound, C13H15NO3, contains a chiral cis-disubstituted oxazine linked to a phenyl ring at the C-2 atom. The racemic crystal structure is stabilized by both intra- and inter­molecular C—H⋯O hydrogen bonds.

The thermostable catechol 2,3-dioxygenase of Bacillus stearothermophilus has been crystallized. The crystal is probably in the space group I 222 with unit-cell dimensions of a = 70.87, b = 74.60 and c = 133.69 Å. A native data set has been collected with a completeness of 96% at 2.22 Å resolution and an R merge value of 0.091.

The title compound, C23H17NO2, was prepared by reacting 10-(3-amino­benzyl­idene)anthrone and acetic anhydride in the presence of pyridine. X-ray crystal structure analysis shows that the three rings of the anthraquinone system are not coplanar because of steric inter­actions with the benzyl­idene group.

The title compound, dimethyl 10b'-(4-fluorostyryl)-8',9'-di-methoxy-4-nitro-5',6'-dihydrospiro[9H-fluorene-9,1'(10b'H)-pyrrolo[2,1-a]isoquinoline]-2'.3'-dicarboxylate. C 38 H 31 FN 2 O 8 , is a new photochromic tetrahydroindolizine. One of the C-C bonds at the spiro C atom is very long [1.630 (2) A], thus explaining the photochromic behaviour.

The title compound, C21H28N4, was synthesized. It is an unusual example of a Z′ = 4 structure without obvious pseudosymmetry. The mol­ecules are linked by numerous C—H⋯N and C—H⋯π hydrogen bonds; there are many H⋯H short contacts.

The title compound, 2,2′-(2,4,8,10-tetra­thia­spiro­[5.5]­undec­ane-3,9-diyl­idene)­bis­(propane­di­nitrile), C13H8N4S4, has been designed and synthesized for use as a potential new organic molecular electronic material. The spiro-annulated structure has twofold symmetry and is formed by two equal push–pull ethyl­ene units, with the cyclo­alkyl­thio groups as electron donors and the cyano groups as electron acceptors. The intermolecular S⋯N non-bonded separation within a layer in the lattice is 3.296 (6) A, indicating a strong intermolecular interaction between the cyano groups and the S atoms, while the S atoms in two neighbouring mol­ecules have a shortest S⋯S contact of 3.449 (3) A. In addition, attractive C—H⋯N and C—H⋯S interactions bridge adjacent mol­ecules either within a layer or between layers. In short, these four types of intermolecular interactions combine to form an extended three-dimensional network in the lattice, resulting in a highly ordered array of molecular packing.

Thermostable alkaline phosphatase from Thermus sp. 3041 has been expressed in Escherichia coli, purified and crystallized. The crystals belong to space group P2(1)22(1), with unit-cell parameters a = 57.7, b = 69.9, c = 111.5 A. Diffraction data were collected to 2.54 A with a completeness of 91.1% (87.8% for the last shell), an R(merge) value of 0.105 (0.312) and an I/sigma(I) value of 9.5 (3.6).

The title compound, C37H37N3O5, was synthesized as a key inter­mediate in the total synthesis of d-biotin and was crystallized from 2-propanol. It contains one chiral center in the pyrrole ring, where the absolute configuration is known from the synthesis, and from which the two other chiral centers in the imidazolidine ring could be determined. An intra­molecular O—H⋯O and inter­molecular C—H⋯O hydrogen bonds help to construct the three-dimensional network.

Slow diffusion of hexane into an ethyl acetate solution of the title compound, C23H27NO4, gave X-ray quality crystals. In the crystal structure, inter­molecular O—H⋯O hydrogen bonds link mol­ecules into one-dimensional chains. In addition, weak C—H⋯O hydrogen bonds help stabilize the crystal structure.