[Fluorescence Spectroscopic Studies on Binding of 20 (S)-Protopanaxatriol with Bovine Serum Albumin].

The interaction between 20(S)-protopanaxatriol (PPT) and bovine serum albumin ( BSA) was studied with fluorescence quenching technique and ultra-violet absorption spectroscopy. The results indicated that PPT led to the intrinsic fluorescence quenching of BSA through a static quenching process .The binding constants of PPT with BSA obtained with fluorescence quenching method were calculated as 0.926 3×10(3) (298 K), 0.618 2×10(3) (308 K), 0.414 4×10(3) L·mol(-1)(318 K), respectively; while the number binding sites n were close to unity. The results showed that the driving force of the interaction between PPT and BSA was hydrogen bond and Van der Waals force. The result of synchronous fluorescence spectra showed that binding of PPT with BSA could induce conformational changes in BSA, that the part of tryptophan became more closely. According to Föster fluorescence resonance energy transfer theory, the binding distance r and energy-transfer efficiency E were respectively 26.2 nm and 0.32.

Crystal structure of 4-acetamido-benzoic acid monohydrate.

In the title compound, C9H9NO3·H2O, the plane of the acetamide group is oriented at 20.52 (8)° with respect to the benzene ring, whereas the plane of the carb-oxy-lic acid group is essentially coplanar with the benzene ring [maximum deviation = 0.033 (1) Å]. In the crystal, classical O-H⋯O and N-H⋯O hydrogen bonds and weak C-H⋯O hydrogen bonds link the organic mol-ecules and water mol-ecules of crystallization into a three-dimensional supra-molecular architecture.

N-(7-Methyl-1,8-naphthyridin-2-yl)acetamide-acetic acid (1/1).

In the title adduct, C11H11N3O·C2H4O2, all non-H atoms of the acetamide mol-ecule are roughly coplanar, with an r.m.s. deviation of 0.0720 Å. The dihedral angle between the ring plane and the acetamide group is 8.5 (2)°. In the crystal, O-H⋯N and N-H⋯O hydrogen bonds link the acetamide and acetic acid mol-ecules.

N-(7-Dibromo-methyl-5-methyl-1,8-naphthyridin-2-yl)acetamide-pyrrolidine-2,5-dione (1/1).

In the title co-crystal, C(12)H(11)Br(2)N(3)O·C(4)H(5)NO(2), the naphthyridine derivative and the pyrrolidine-2,5-dione mol-ecules have crystallographic mirror-plane symmetry with all non-H atoms, except the Br atom, located on the mirror plane. In the crystal, N-H⋯N, N-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into heterodimers. These dimers are further linked into a one-dimensional structure along [010] by weak C-Br⋯O inter-actions [Br⋯O = 3.028 (5) Šand C-Br⋯O = 158.52 (4)°].

Solubility and biological activity enhancement of docetaxel via formation of inclusion complexes with three alkylenediamine-modified ß-cyclodextrins.

Docetaxel (DTX) is an effective and commonly used chemotherapeutic drug for cancer. However, its efficacy is greatly compromised because of its toxicity and poor water solubility. In order to overcome these disadvantages, three inclusion complexes between DTX and alkylenediamine-modified ß-cyclodextrins (H1-3) with ethylene, propylene and butylene segments were prepared and characterized. The phase solubility studies demonstrated that the stoichiometry of the inclusion complexes between H1-3 and DTX were 1 : 1. The binding abilities of host H1-3 towards DTX decrease in the following order: H3 > H2 > H1, which had good consistency with the decreasing alkylene lengths of these hosts. The water solubility of DTX is remarkably increased 216, 242 and 253 times after forming inclusion complexes with H1-3, respectively. In vitro release studies of DTX from H1-3/DTX into NaAc-HAc buffer solution (pH 5.0) or PBS (pH 7.4) exhibited a preliminary stage burst effect and followed by a slow drug release. The cytotoxicity studies revealed that the H1-3/DTX inclusion complexes exhibited better cytotoxicity profiles against MCF-7, SW480 and A-549 cells than that of DTX. Furthermore, compared with the treatment of DTX, the H1/DTX inclusion complex significantly increased the cell apoptosis percentage from 17.2% to 30.2% (5 µg mL-1), 19.0% to 31.0% (10 µg mL-1), and 19.3% to 32.2% (15 µg mL-1), respectively. These results will provide useful information for H1-3/DTX inclusion complexes as safe and efficient anticancer drug formulations.

Experimental and molecular docking investigation of the inclusion complexes between 20(S)-protopanaxatriol and four modified ß-cyclodextrins.

20(S)-Protopanaxatriol (PPT) is a type of ginsenoside isolated from panax notoginseng or ginseng, which is an essential ingredient in functional food, healthcare products and traditional medicine. However, the research and development of PPT are restricted due to its poor solubility. To circumvent the associated problems, a novel bridged-bis [6-(2,2'-(ethylenedioxy) bis (ethylamine))-6-deoxy-ß-CD] (H4) was successfully synthesized. The four inclusion complexes of the mono-[6-(1,4-butanediamine)-6-deoxy-ß-CD] (H1), mono-[6-(2,2'-(ethylenedioxy) bis (ethylamine)-6-deoxy-ß-CD] (H2) and their corresponding bridged bis(ß-CD)s (H3, H4) with PPT were prepared and studied by UV, 1H NMR, 2D ROESY, FT-IR, XRD and SEM technology. The UV-spectrometric titration showed that H1-4 and PPT formed 1:1 inclusion complexes and the binding constants were 297.61, 322.25, 937.88 and 1742 M-1, respectively. It was further revealed that the size/shape-matching relationship, hydrophobic interactions and hydrogen bond interactions play the crucial role in determining the stability of H1-4/PPT inclusion complexes. The solubility of PPT was evidently enhanced by193, 265, 453 and 593 times after the formation of inclusion complexes with H1-4, respectively. Furthermore, molecular docking was used to verify the inclusion mode of H4/PPT inclusion complex and also to investigate the stability of H4/PPT in water phase. The molecular simulation results agreed well with the experimental results. This research provides an effective way to obtain novel PPT-based functional food and healthcare products.

[Molecular geometries and theoretical electronic spectra of four 1,8-naphthyridine derivatives].

The molecular geometries of four 2,4-dimethyl-7-amino-1,8-naphthyridine derivatives were optimized with B3LYP/6-31G(d) method. The energies of their frontier molecular orbitals and the molecular structures were investigated theoretically. The theoretical electronic spectra were calculated with TD-DFT in gas phase, PCM-TD-B3LYP/6-31 + G(d) and semiempirical ZINDO in CH2 Cl2 solution. The influences of solvent model and calculation methods on the electronic absorption spectra were also probed. The calculated results show that delocalized pi bonds exist in the four 1,8-naphthyridine derivatives, and their energy gaps (deltaE) between HOMO and LUMO are relatively small. The variation in their deltaE values gives a consistent trend with that of their electronic absorption with lambda(max). Theoretical spectra achieved prove that their absorptions are red-shifted when the delocalization of pi electrons is enhanced or the capability to donate electron by a substituted group is increased. The maximum absorption peaks of the four derivatives originate from pi (HOMO) --> pi * (LUMO) transition. The spectra calculated at the PCM-B3LYP/6-31 + G(d) level have little difference from experimental results: the differences in wavelength are 2.6, 10.3, 5.3 and 6.9 nm, whereas those in energies are 0.03, 0.09, 0.04 and 0.08 eV, respectively. The obtained results suggest that electronic spectra calculated by TD-DFT on the bases of geometries optimized with B3LYP/6-31(d) are in agreement with experimental ones, and can account for the different spectroscopic properties of the four 1,8-naphthyridine derivatives.

[Synthesis and spectra of copper(I) bromide complex with N, N-bis[(diphenylphosphino) methyl]-2-pyridinylamine].

A new ligand N, N-bis[(diphenylphosphino)methyl]-2-pyridinylamine (L) and its luminescent dinuclear copper(I) complex [CuBrL]1 (1) were synthesized and characterized by mass spectrometry, elemental analysis, NMR and electronic spectroscopies. The structure of complex 1 was determined by X-ray crystal analysis to be a dinuclear complex with a pseudo-tetrahedral geometry. The complex 1 crystallizes in a triclinic space group P-1 and has two copper(I ) centers bridged by two halogen ligands to form the dinuclear structure with a four-membered Cu2 Br2 ring. The Cu-Cu distance in complex 1 is 0.306 0 nm which is longer than a sum of Van der Waals radius of two copper( I ) atoms. Therefore there is no substantial interaction between the two copper(I) centers in complex 1. DFT calculations indicate that the electron density of HOMO is distributed mainly over the copper, bromine and phosphorus atoms, while that of LUMO is localized on the ligand. Our work shows that there are two mechanisms to form the the lowest excited state of complex 1, i.e. the metal-to-ligand charge transfer (MLCT) and halogen-to-ligand charge transfer (XLCT).

Crystal structure of 9-(di-bromo-meth-yl)-1,1-di-fluoro-3,7-dimethyl-1H-[1,3,5,2]oxadi-aza-borinino[3,4-a][1,8]naphthyridin-11-ium-1-uide.

The mol-ecule of the title 1,8-naphthyridine-BF2 derivative, C12H10BBr2F2N3O, is located on a mirror plane running parallel to the entire ring system and the attached methyl C atoms. Individual mol-ecules are stacked along the b-axis direction. The cohesion in the crystal structure is accomplished by C-H⋯F hydrogen bonds and additional off-set π-π inter-actions [centroid-to-centroid distance = 3.6392 (9) Å, slippage 0.472 Å], leading to the formation of a three-dimensional supra-molecular network.

Cu(I) and Pb(II) complexes containing new tris(7-naphthyridyl)methane derivatives: synthesis, structures, spectroscopy and geometric conversion.

Two novel facial-capping tris-naphthyridyl compounds, 2-chloro-5-methyl-7-((2,4-dimethyl-1,8-naphthyridin-7(1H)-ylidene)(2,4-dimethyl-1,8-naphthyridin-7-yl))methyl-1,8-naphthyridine (L(1)) and 2-chloro-7-((2-methyl-1,8-naphthyridin-7(1H)-ylidene)(2-methyl-1,8-naphthyridin-7-yl))methyl-1,8-naphthyridine (L(2)), as well as their Cu(i) and Pb(ii) complexes, [CuL(a)(PPh(3))]BF(4) (1) (PPh(3) = triphenylphosphine, L(a) = bis(2,4-dimethyl-1,8-naphthyridin-7-yl)(2-chloro-5-methyl-1,8-naphthyridin-7-yl)methane), [CuL(b)(PPh(3))]BF(4) (2) (L(b) = bis(2-methyl-1,8-naphthyridin-7-yl)(2-chloro-1,8-naphthyridin-7-yl)methane), [Pb(OL(a))(NO(3))(2)] (3) (OL(a) = bis(2,4-dimethyl-1,8-naphthyridin-7-yl)(2-chloro-5-methyl-1,8-naphthyridin-7-yl)methanol) and [Pb(L(b))(2)][Pb(CH(3)OH)(NO(3))(4)] (4), have been synthesized and characterized by X-ray diffraction analysis, MS, NMR and elemental analysis. The structural investigations revealed that the transfer of the H-atom at the central carbon to an adjacent naphthyridine-N atom affords L(1) and L(2) possessing large conjugated architectures, and the central carbon atoms adopt the sp(2) hybridized bonding mode. The reversible hydrogen transfer and a geometric configuration conversion from sp(2) to sp(3) of the central carbon atom were observed when Pb(II) and Cu(I) were coordinated to L(1) or L(2). The molecular energy changes accompanying the hydrogen migration and titration of H(+) to different receptor-N at L(1) were calculated by density functional theory (DFT) at the SCRF-B3LYP/6-311++G(d,p) level in a CH(2)Cl(2) solution, and the observed lowest-energy absorption and emission for L(1) and L(2) can be tentatively assigned to an intramolecular charge transfer (ICT) transition in nature.

Conjugation effect of the bridging ligand on the CO2 reduction properties in difunctional photocatalysts.

The photocatalytic activity for CO(2) reduction and optical and electrochemical properties of two Ru(II)-Re(I) binuclear complexes [Ru(dmb)(2)LRe(CO)(3)Cl](2+) (Ru-Re and Ru=Re, dmb = 4,4'-dimethyl-2,2'-bipyridine) with 1,2-bis(4'-methyl-2,2'-bipyridyl-4-yl)ethane and 1,2-bis(4'-methyl-2,2'-bipyridyl-4-yl)ethene as bridging ligands have been investigated. The conjugation content of the bridging ligands plays an important role in the photocatalytic behavior: a saturated linkage exhibited more efficient than the conjugated.

A flexible 1,8-naphthyridyl derivative and its Zn(II) complexes: synthesis, structures, spectroscopic properties and recognition of Cd(II).

A flexible ligand bis(7-methyl-1,8-naphthyridine-2-ylamino)methane (), having kappa(4)-chelating and kappa(2)-bridging modes, and its intriguing structural complexes of Zn(II) with mu-OH, kappa(1)-OAc, mu-kappa(1)-OAc and mu-kappa(2)-OAc ligands, [Zn(2)()(2)(OH)](ClO(4))(3) (), [Zn(4)()(2)(OAc)(6)(OH)(2)].CH(2)Cl(2) (.CH(2)Cl(2)) and [Zn(5)()(2)(OAc)(10)](n).4nH(2)O (.4H(2)O) were synthesized and their structures were determined by X-ray crystallography. These compounds exhibited intense blue fluorescent emissions with a lambda(max) in the range of 380-410 nm in CH(2)Cl(2), CH(3)CN and CH(3)OH solutions, and solid-state emissions centered at 416, 463, 490 and 451 nm were observed for the compounds , , and at room temperature, respectively. The investigated fluorescence properties of associated with various metal ions showed that the fluorescence enhancement of with Cd(II) was more sensitive than with other interfering cations.