4-Amino-N-(2,3-di-hydro-1,3-thia-zol-2-yl-idene)benzene-sulfonamide-2,4,6-tris-(pyr-idin-2-yl)-1,3,5-triazine (1/1).

The sulfa-thia-zole mol-ecule in the title 1:1 co-crystal, C9H9N3O2S2·C18H12N6, adopts an approximate L-shape [dihedral angle between the five- and six-membered rings = 86.20 (9)°] and features an intra-molecular hypervalent S⋯O inter-action [2.8666 (15) Å]. Overall, the triazine mol-ecule has the shape of a disk as the pendant pyridine rings are relatively close to coplanar with the central ring [dihedral angles = 18.35 (9), 6.12 (9) and 4.67 (9)°]. In the crystal packing, a linear supra-molecular chain aligned along [01-1] is formed as a result of amino-pyridyl N-H⋯N hydrogen bonding with syn-disposed pyridyl mol-ecules of one triazine, and amine-pyridyl N-H⋯N hydrogen bonding with the third pydridyl ring of a second triazine mol-ecule. A three-dimensional architecture arises as the chains are connected by C-H⋯O inter-actions.

4-Amino-N-(4,6-di-methyl-pyrimidin-2-yl)benzene-sulfonamide-1,4-di-aza-bicyclo-[2.2.2]octane (2/1).

The asymmetric unit of the title co-crystal, C12H14N4O2S·0.5C6H12N2, comprises the sulfonamide mol-ecule and half a mol-ecule of 1,4-di-aza-bicyclo-[2.2.2]octane (DABCO), the latter being disposed about a crystallographic twofold rotation axis. In the sulfonamide mol-ecule, the aromatic rings are almost perpendicular to one another [dihedral angle = 75.01 (8)°]. In the crystal, mol-ecules are connected into a three-mol-ecule aggregate via amide-DABCO N-H⋯N hydrogen bonds, and these are connected into a three-dimensional architecture via amino-DABCO N-H⋯O and amino-pyrimidine N-H⋯N hydrogen bonds.

Bis(2,9-dimethyl-1,10-phenanthrolin-1-ium) 2,5-di-carb-oxy-benzene-1,4-di-carb-oxyl-ate-2,9-dimethyl-1,10-phenanthroline-benzene-1,2,4,5-tetra-carb-oxy-lic acid (1/2/1).

The asymmetric unit of the title co-crystal, 2C14H13N2 (+)·C10H4O8 (2-)·2C14H12N2·C10H6O8, comprises a 2,9-dimethyl-1,10-phenanthrolin-1-ium cation (Me2PhenH(+)) and a 2,9-dimethyl-1,10-phenanthroline mol-ecule (Me2Phen), each in a general position, and half each of a 2,5-di-carb-oxy-benzene-1,4-di-carboxyl-ate dianion (LH2 (2-)) and a benzene-1,2,4,5-tetra-carb-oxy-lic acid mol-ecule (LH4), each being disposed about a centre of inversion. Small twists are evident in the dianion [the C-C-C-O torsion angles are 168.41 (18) and 16.2 (3)°], whereas a major twist is found for one carb-oxy-lic acid group in the neutral mol-ecule [C-C-C-O = 66.3 (2) and 18.2 (3)°]. The most prominent feature of the crystal packing is the formation of linear supra-molecular chains along [001] mediated by charge-assisted O-H⋯O(-) hydrogen bonding between alternating LH4 and LH2 (2-). These are connected to the Me2PhenH(+) and Me2Phen species by N-H⋯O and O-H⋯N hydrogen bonds, respectively. A three-dimensional architecture is formed by C-H⋯O and π-π inter-actions [inter-centroid distance = 3.5337 (17) Å].

tert-But-yl(2-hy-droxy-eth-yl)aza-nium 4-[(1,3-thia-zol-2-yl-aza-nid-yl)sulfon-yl]aniline.

Two pairs of independent cations and anions comprise the asymmetric unit of the title salt, C(6)H(16)NO(+)·C(9)H(8)N(3)O(2)S(2) (-). The cations are virtually superimposable and each exhibits a gauche disposition of the hy-droxy O and ammonium N atoms [the O-C-C-N torsion angles are 55.5 (3) and 57.5 (3)°]. Significant differences are seen in the mol-ecular structures of the anions as seen in the S-N-C-S [1.1 (3) and 32.9 (3)°] and C-S-N-C [-69.7 (2) and 91.4 (2)°] torsion angles. Despite the variations in conformation, intra-molecular hypervalent S⋯O inter-actions persist in each anion [3.078 (2) and 2.8730 (19) Å]. In the crystal, supra-molecular double layers are formed in the bc plane, being sustained by O-H⋯N, N-H⋯O and N-H⋯N hydrogen bonding. These are connected along the a axis via C-H⋯O inter-actions.

2-Amino-benzoic acid-4-(pyridin-4-yl-disulfan-yl)pyridine (1/1).

The title 1:1 co-crystal, C(7)H(7)NO(2)·C(10)H(8)N(2)S(2), features a highly twisted 4-(pyridin-4-yldisulfan-yl)pyridine mol-ecule [dihedral angle between the pyridine rings = 89.06 (10)°]. A small twist is evident in the 2-amino-benzoic acid mol-ecule, with the C-C-C-O torsion angle being -7.7 (3)°. An N-H⋯O hydrogen bond occurs in the 2-amino-benzoic acid mol-ecule. In the crystal, mol-ecules are linked by O-H⋯N and N-H⋯N hydrogen bonds into a supra-molecular chain along the b axis. These are connected into layers by π-π inter-actions occurring between pyridine rings [centroid-centroid distance = 3.8489 (15) Å]. The layers are connected along the a axis by C-H⋯O contacts. The crystal studied was a racemic twin.

4-Aza-1-azoniabicyclo-[2.2.2]octa-ne-2-amino-benzoate-2-amino-benzoic acid (1/1/1).

A 4-aza-1-azoniabicyclo-[2.2.2]octane cation, a 2-amino-benzoate anion and a neutral 2-amino-benzoic acid mol-ecule comprise the asymmetric unit of the title compound, C(6)H(13)N(2) (+)·C(7)H(6)NO(2) (-)·C(7)H(7)NO(2). An intra-molecular N-H⋯O hydrogen bond occurs in the anion and in the neutral 2-amino-benzoic acid mol-ecule. The cation provides a charge-assisted N-H⋯O hydrogen bond to the anion, and the 2-amino-benzoic acid mol-ecule forms an O-H⋯N hydrogen bond to the unprotonated amino N atom in the cation. In this way, a three-component aggregate is formed. These are connected into a three-dimensional network by amino-carboxyl-ate N-H⋯O hydrogen bonds. N-H⋯N hydrogen bonds are also observed.

2,2'-(Disulfanedi-yl)dibenzoic acid-2,9-dimethyl-phenanthroline-tetra-hydro-furan (1/2/1).

The asymmetric unit of the title co-crystal solvate, C(14)H(10)O(4)S(2)·2C(14)H(12)N(2)·C(4)H(8)O, comprises a 2,2'-(disulfanedi-yl)dibenzoic acid mol-ecule, two mol-ecules of 2,9-dimethyl-phenanthroline and a tetra-hydro-furan (THF) solvent mol-ecule. Each end of the twisted diacid [dihedral angle between the benzene rings = 74.33 (17)°] forms a strong O-H⋯N hydrogen bond with a 2,9-dimethyl-phenanthroline mol-ecule, forming a trimeric aggregate. The crystal structure comprises layers of acid and THF mol-ecules, and layers of 2,9-dimethyl-phenanthroline mol-ecules that alternate along the a axis, the main connections between them being of the type C-H⋯O.

2-Phenyl-acetic acid-(E,E)-4,4'-(hydra-zinediylidene)dipyridine (2/1).

The asymmetric unit of the title co-crystal, C(12)H(10)N(4)·2C(8)H(8)O(2), comprises a single mol-ecule of 2-phenyl-acetic acid and half a mol-ecule of 4-pyridine-aldazine as this is situated about a centre of inversion. Mol-ecules are connected into a three component aggregate via O-H⋯N hydrogen bonds. As the carb-oxy-lic acid group is almost normal to the plane through the benzene ring to which it is attached [C-C-C-C = 93.7 (3) °], and the 4-pyridine-aldazine mol-ecule is planar (r.m.s. deviation of the 16 non-H atoms = 0.010 Å), the overall shape of the aggregate is that of an extended chair. In the crystal packing, layers of three component aggregates stack along the c axis.

1,2,4,5-Tetra-fluoro-3,6-diiodo-benzene-4-(pyridin-4-ylsulfan-yl)pyridine (1/1).

The asymmetric unit of the title 1:1 adduct, C(10)H(8)N(2)S·C(6)F(4)I(2), comprises a half-mol-ecule of 1,2,4,5-tetra-fluoro-3,6-diiodo-benzene, and half a 4-(pyridin-4-ylsulfan-yl)pyridine mol-ecule. The former is completed by crystallographic inversion symmetry, the latter by twofold symmetry, with the S atom lying on the rotation axis. The almost planar 1,2,4,5-tetra-fluoro-3,6-diiodo-benzene mol-ecule (r.m.s. deviation of all 12 atoms = 0.016 Å) and twisted 4-(pyridin-4-ylsulfan-yl)pyridine mol-ecule [dihedral angle between pyridyl rings = 54.88 (13)°] are connected by N⋯I inter-actions [2.838 (4) Å], generating a supra-molecular chain with a step-ladder topology. These chains are connected in the crystal by C-H⋯F and C-H⋯π(pyrid-yl) inter-actions.

2-Phenyl-acetic acid-3-{(E)-2-[(E)-pyridin-3-yl-methyl-idene]hydrazin-1-ylidenemeth-yl}pyridine (2/1).

The asymmetric unit of the title 1:2 adduct, C(12)H(10)N(4)·2C(8)H(8)O(2), comprises a single mol-ecule of 2-phenyl-acetic acid and half a mol-ecule of 3-pyridine-aldazine; the latter is completed by crystallographic inversion symmetry. In the crystal, mol-ecules are connected into a three-component aggregate via O-H⋯N hydrogen bonds. As the carboxyl group lies above the plane through the benzene ring to which it is attached [C-C-C-C = 62.24 (17)°] and the 4-pyridine-aldazine mol-ecule is almost planar (r.m.s. deviation of the 16 non-H atoms = 0.027 Å), the overall shape of the aggregate is that of a flattened extended chair. Layers of these aggregates are connected by C-H⋯O and C-H⋯π inter-actions and stack parallel to (220).

Benzoic acid-2,9-dimethyl-phenanthroline (1/1).

The constituents of the title 1:1 co-crystal, C(7)H(6)O(2)·C(14)H(12)N(2), are connected into dimeric aggregates by a bifurcated O-H⋯N hydrogen bond; the hydroxyl-H atom is hydrogen bonded to the two N atoms of the 2,9-dimethyl-phenanthroline. The hydrogen-bonded residues are almost orthogonal to each other [dihedral angle = 78.56 (7) °]. In the crystal packing, the aggregates are assembled into layers in the bc plane by π⋯π inter-actions [ring centroid⋯ring centroid distance = 3.5577 (16) Å] involving the pyridyl rings, and C-H⋯π contacts involving the phenanthroline-H atom and the phenyl ring of the acid.

2-(4-Chloro-phen-yl)acetic acid-2-{(E)-[(E)-2-(2-pyridyl-methyl-idene)hydrazin-1-yl-idene]meth-yl}pyridine (1/1).

In the crystal of the title 1:1 adduct, C(8)H(7)ClO(2)·C(12)H(10)N(4), the components are linked by an O-H⋯N hydrogen bond between the carb-oxy-lic acid and one of the pyridine N atoms. In the acid, the carb-oxy-lic acid group is approximately normal to [dihedral angle = 72.9 (2)°] but twisted with respect to the plane through the benzene ring [C-C-C-O torsion angle = 25.4 (5)°]. The base is roughly planar [dihedral angle between rings = 12.66 (15)°; r.m.s. deviation of the 16 non-H atoms = 0.107 Å] and the conformations about both imine bonds are E. The dimeric aggregates are linked into a supra-molecular layer in the ab plane by C-H⋯O inter-actions.

4-Amino-N-(4,6-dimethyl-pyrimidin-2-yl)benzene-sulfonamide-benzoic acid (1/1).

The constituents of the title co-crystal, C(12)H(14)N(4)O(2)S·C(7)H(6)O(2), are connected by an eight-membered hetero-synthon {⋯NCNH⋯OCOH}, whereby the carb-oxy-lic acid forms donor and acceptor hydrogen bonds with a pyrimidine N atom and the adjacent amine, respectively. The dimeric aggregates thus formed are arranged in rows with their terminal NH(2) groups forming N-H⋯O hydrogen bonds with neighbouring aggregates to form a two-dimensional array in the ac plane with an overall T-shaped topology. Layers inter-digitate along the b axis being connected by C-H⋯O, C-H⋯π and π-π [centroid-centroid distance = 3.6316 (19) Å] inter-actions.

Benzoic acid-2-{(E)-[(E)-2-(2-pyridyl-methyl-idene)hydrazin-1-yl-idene]meth-yl}pyridine (2/1).

The asymmetric unit of the title cocrystal, C(12)H(10)N(4)·2C(7)H(6)O(2), comprises a single mol-ecule of benzoic acid and one half-mol-ecule of 2-pyridine-aldazine situated about a centre of inversion. The carboxyl group is coplanar with the benzene ring to which it is connected [O-C-C-C = -172.47 (12)°] and similarly, the 2-pyridine-aldazine mol-ecule is planar (r.m.s. deviation of the 16 non-H atoms = 0.017 Å). In the crystal, mol-ecules are connected into a non-planar three-mol-ecule aggregate [dihedral angle between the benzene and pyridyl ring connected by the hydrogen bond = 61.30 (7)°] with a twisted Z-shape. Layers of 2-pyridine-aldazine mol-ecules in the ab plane are sandwiched by benzoic acid mol-ecules being connected by O-H⋯N and C-H⋯O inter-actions, the latter involving the carbonyl O atom so that each benzoic acid mol-ecule links three different 2-pyridine-aldazine mol-ecules. Inter-digitated layers stack along the c axis.

1,2,4,5-Tetra-fluoro-3,6-diiodo-benzene-2,3-bis-(pyridin-2-yl)pyrazine (1/1).

The components of the title 1:1 co-crystal, C(14)H(10)N(4)·C(6)F(4)I(2), are connected via an N⋯I [2.959 (4) Å] halogen bond, in which the N atom is part of the relatively electron-rich pyrazine ring. The C(6)F(4)I(2) mol-ecule is almost planar [r.m.s. deviation = 0.038 Å] but there are significant twists in the pyrazine derivative, as seen in the dihedral angles [31.3 (2) and 54.6 (2)°] formed between the pendant pyridyl rings and the central pyrazine ring. The bimolecular aggregates are sustained in the crystal by C-H⋯F and π-π inter-actions [ring centroid(pyrid-yl)-ring centroid(benzene) = 3.678 (3) Å].

Benzoic acid-4-{(1E)-[(E)-2-(pyridin-4-yl-methyl-idene)hydrazin-1-yl-idene]meth-yl}pyridine (2/1).

In the title co-crystal, C(12)H(10)N(4)·2C(7)H(6)O(2), the complete 4-pyridine-aldazine mol-ecule is generated by a crystallographic centre of inversion. In the crystal, mol-ecules are connected into a three component aggregate via O-H⋯N hydrogen bonds. As both the benzoic acid [O-C-C-C torsion angle = 174.8 (2)°] and 4-pyridine-aldazine (r.m.s. deviation of the 16 non-H atoms = 0.041 Å) mol-ecules are almost planar, the resulting three-component aggregate is essentially planar. The crystal packing comprises layers of the three-component aggregates of alternating orientation stacked along the b axis; the connections between the mol-ecules are of the types C-H⋯π and π-π [pyridine-benzene centroid-centroid distance = 3.787 (4) Å].

Insights from xanthine and uracil DNA glycosylase activities of bacterial and human SMUG1: switching SMUG1 to UDG.

Single-strand-selective monofunctional uracil DNA glycosylase (SMUG1) belongs to Family 3 of the uracil DNA glycosylase (UDG) superfamily. Here, we report that a bacterial SMUG1 ortholog in Geobacter metallireducens (Gme) and the human SMUG1 enzyme are not only UDGs but also xanthine DNA glycosylases (XDGs). In addition, mutational analysis and molecular dynamics (MD) simulations of Gme SMUG1 identify important structural determinants in conserved motifs 1 and 2 for XDG and UDG activities. Mutations at M57 (M57L) and H210 (H210G, H210M, and H210N), both of which are involved in interactions with the C2 carbonyl oxygen in uracil or xanthine, cause substantial reductions in XDG and UDG activities. Increased selectivity is achieved in the A214R mutant of Gme SMUG1, which corresponds to a position involved in base flipping. This mutation results in an activity profile resembling a human SMUG1-like enzyme as exemplified by the retention of UDG activity on mismatched base pairs and weak XDG activity. MD simulations indicate that M57L increases the flexibility of the motif 2 loop region and specifically A214, which may account for the reduced catalytic activity. G60Y completely abolishes XDG and UDG activity, which is consistent with a modeled structure in which G60Y blocks the entry of either xanthine or uracil to the base binding pocket. Most interestingly, a proline substitution at the G63 position switches the Gme SMUG1 enzyme to an exclusive UDG as demonstrated by the uniform excision of uracil in both double-stranded and single-stranded DNA and the complete loss of XDG activity. MD simulations indicate that a combination of a reduced free volume and altered flexibility in the active-site loops may underlie the dramatic effects of the G63P mutation on the activity profile of SMUG1. This study offers insights on the important role that modulation of conformational flexibility may play in defining specificity and catalytic efficiency.

N-(4,6-Dimethyl-pyrimidin-2-yl)-4-(oxolan-2-ylamino)benzene-sulfonamide.

The title compound, C(16)H(20)N(4)O(3)S, adopts an l-shaped conformation, as seen by the dihedral angle of 76.93 (7)° formed between the two aromatic rings. The most notable feature of the crystal packing is the formation of N-H⋯O and N-H⋯N hydrogen bonds that lead to supra-molecular chains orientated along the b axis.

4,4'-Bipyridine-pyroglutamic acid (1/2).

In the title co-crystal, C(10)H(8)N(2)·2C(5)H(7)NO(3), the 4,4'-bipyridine mol-ecule [dihedral angle between the pyridine rings = 36.33 (11)°] accepts O-H⋯N hydrogen bonds from the two pyroglutamic (pga) acid mol-ecules. The pga mol-ecules at each end of the trimeric aggregate self-associate via centrosymmetric eight-membered amide {⋯HNCO}(2) synthons, so that the crystal structure comprises one-dimensional supra-molecular chains propagating in [13]. C-H⋯O and π-π stacking inter-actions [centroid-centroid separation = 3.590 (2) Å] consolidate the structure.

Electronic structure and normal vibrations of CH3(OCH2CH2)nOCH3-M+-CF3SO3- (n = 2-4, M = Li, Na, and K).

Electronic structure and the vibrational frequencies of CH(3)(OCH(2)CH(2))(n)OCH(3)-M(+)-CF(3)SO(3)(-) (n = 2-4, M = Li, Na, and K) complexes have been derived from ab initio Hartree-Fock calculations. The metal ion shows varying coordination from 5 to 7 in these complexes. In tetraglyme-lithium triflate, Li(+) binds to one of the oxygens of CF(3)SO(3)(-) (triflate or Tf(-)) unlike for potassium or sodium ions, which possess bidentate coordination. Structures of glyme-MTf complexes thus derived agree well with those determined from X-ray diffraction experiments. The metal ion binds more strongly to ether oxygens of tetraglyme than its di- or triglyme analogues and engenders contraction of SO (for oxygens binding to metal ion) bonds with consequent frequency upshift for the corresponding vibration in the complex relative to those in the free MTf ion pairs. Complexation of the diglyme with LiTf engenders the largest downshift (91 cm(-1)) for the SO(2) stretching vibration of the free anion, which suggests stronger binding of lithium to the diglyme than the tri- (79 cm(-1)) or tetraglyme (70 cm(-1)). A frequency shift in the opposite direction for the SO (where oxygens do not coordinate to the metal) and CF(3) stretchings, which stems from the ion-polymer and anion-ion interactions, has been noticed. These frequency shifts have been analyzed using natural bond orbital analysis and difference electron density maps coupled with molecular electron density topography.