Methoxy-phenyl substituted ansa-titanocenes as potential anti-cancer drugs derived from fulvenes and titanium dichloride

Starting from 6-(4'-methoxyphenyl)fulvene (1a), 6-(2',4',6'-trimethoxyphenyl)fulvene (1b), or 6-(3',5'-dimethoxyphenyl)fulvene (1c), [1,2-di(cyclopentadienyl)-1,2-di(4'-methoxyphenyl)-ethanediyl] titanium dichloride (2a), [1,2-di(cyclopentadienyl)-1,2-bis(2',4',6'-trimethoxyphenyl)-ethanediyl] titanium dichloride (2b), and [1,2-di(cyclopentadienyl)-1,2-bis(3',5'-dimethoxyphenyl)-ethanediyl] titanium dichloride (2c) were synthesised. When titanocenes 2a-c were tested against pig kidney carcinoma cells (LLC-PK) inhibitory concentrations (IC50) of 2.8 x 10(-4), 3.6 x 10(-4) and 2.1 x 10(-4) M, respectively, were observed.     

Novel benzyl-substituted molybdocene anticancer drugs

From the reaction of 6-(p-methoxyphenyl) fulvene (1a), 6-(3,4-dimethoxyphenyl) fulvene (1b) and 6-(3,4,5-trimethoxyphenyl) fulvene (1c) with LiBEt₃H, lithiated cyclopentadienide intermediates (2a-c) were synthesised. These intermediates were then transmetallated to molybdocene using MoCl₄ (synthesized in situ) to yield the benzyl-substituted molybdocenes bis-[(p-methoxybenzyl)cyclopentadienyl] molybdenum (IV) dichloride (3a), bis-[(3,4-dimethoxybenzyl)cyclopentadienyl] molybdenum (IV) dichloride (3b), and bis-[(3,4,5-trimethoxybenzyl)cyclopentadienyl] molybdenum (IV) dichloride (3c). The molybdocene 3a was characterised by single crystal X-ray diffraction. All three molybdocenes had their cytotoxicity investigated through MTT based preliminary in vitro testing on the human renal cell line Caki-1 in order to determine their IC50 values and compare them with the corresponding titanocene and vanadocene dichloride derivatives. Molybdocenes 3b-c were found to have the same IC50 values of 290 μM, while 3a yielded a value of 84 μM, respectively     

Pseudo-halide derivatives of titanocene: synthesis and cytotoxicity studies

The well-known anticancer drug candidate bis-[(p-methoxybenzyl)cyclopentadienyl] titanium(IV) dichloride (Titanocene ) was reacted with sodium azide or potassium cyanate, thiocyanate or selenocyanate in order to give pseudo-halide analogues of Titanocene . and were characterised by single crystal X-ray diffraction, which confirmed the expected nitrogen binding of the cyanate and thiocyanate to the titanium centre. All four titanocenes had their cytotoxicity investigated through preliminary in vitro testing on the LLC-PK (pig kidney epithelial) cell line in an MTT based assay in order to determine their IC50 values. Titanocenes were found to have IC50 values of 24 (± 8) μM, 101 (± 14) μM, 54 (± 21) μM and 27 (± 4) μM respectively. All four titanocene derivatives show significant cytotoxicity improvement when compared to unsubstituted titanocene dichloride and and showed similiar cytotoxic behaviour to Titanocene in vitro.     

Novel derivatives of ansa-titanocenes procured from 6-phenylfulvene: a combined experimental and theoretical study

The previously prepared trans-[(1,2-diphenyl-1,2-dicyclopentadienyl)ethanediyl] titanium(IV) dichloride, [1,2-(Ph)₂C₂H₂{η⁵-C₅H₄}₂]Ti(Cl)₂, was synthesised using an alternative procedure, from which its crystal structure was determined. Using this compound, a variety of other ansa-titanocene derivatives were synthesised by replacement of the chloride ligands with selected substituents. Thus RTi(X)(Y) systems where R=1,2-(Ph)₂C₂H₂η⁵-C₅H₄₂; X=Y=CH₃; X=CH₃, Y=Cl; X=Y=NCS; X=Y=NCO; X=Y=OPh and (X/Y)=O have been synthesised and characterised. DFT calculations were performed on the complexes trans-[(1,2-diphenyl-1,2-dicyclopentadienyl)-ethanediyl] titanium(IV) dichloride, bis-(6,6-diphenylfulvene)titanium and bis-(6,6-diphenylfulvene)iron. This demonstrated the role that the metal centre plays in their formation, generating either an ansa-metallocene, a ‘tucked in’ fulvene complex or a metallocene coordinating fulvene anions.     

Novel achiral titanocene anti-cancer drugs synthesised from bis-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylamino fulvene and lithiated heterocyclic compounds

Abstract From the carbolithiation of 6-bis-N,N-dimethylamino fulvene (3a) and different ortho-lithiated heterocycles (furan, thiophene and N-methylpyrrole), the corresponding lithium cyclopentadienide intermediate (4a–c) was formed. These three lithiated intermediates underwent a transmetallation reaction with TiCl₄ resulting in bis-N,N-dimethylamino-functionalised titanocenes 5a–c. When these titanocenes were tested against LLC-PK cells, the IC₅₀-values obtained were of 240, and 270 μM for titanocenes 5b and 5c, respectively. The most cytotoxic titanocene in this paper, 5a with an IC₅₀-value of 36 μM was found to be approximately six times less cytotoxic than its mono-N,N-dimethylamino substituted analogue Titanocene C (IC₅₀ = 5.5 μM) and almost ten times less cytotoxic than cisplatin, which showed an IC₅₀-value of 3.3 μM, when tested on the LLC-PK cell line. Graphical abstract Bis-(bis- (N,N-dimethylamino)-2-(N′-methylpyrrolyl)methylcyclopentadienyl) titanium (IV) dichloride, {η⁵-C₅H₄-CH[N(CH₃)₂]₂[C₅H₃NCH₃]}₂TiCl₂ was synthesised starting from 6-bis-(N,N-dimethylamino) fulvene and 2-N-methylpyrrolyl lithium. Herein, we present the synthesis and DFT structure of the titanocene and two further derivatives followed by MTT-based cytotoxicity tests on pig kidney epithelial (LLC-PK) cells. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Diheteroarylmethyl substituted titanocenes: A novel class of possible anti-cancer drugs

From the reaction of tert-butyl lithium or n-butyl lithium with N-methylpyrrole (1a), furan (1b) or 2-bromo-thiophen (1c), 2-N-methylpyrrolyl lithium (2a), 2-furyl lithium (2b) or 2-thiophenyl lithium (2c), respectively, was obtained. When reacted with 6-(2-N-methylpyrrolyl) fulvene (3a), 6-(2-furyl) fulvene (3b) or 6-(2-thiophenyl) fulvene (3c), the corresponding lithiated intermediates were formed (4a-c). Titanocenes (5a-c) were obtained through transmetallation with titanium tetrachloride. When these titanocenes were tested against pig kidney epithelial (LLC-PK) cells, inhibitory concentrations (IC₅₀) of 32 μM, 140 μM, and 240 μM, respectively, were observed. These values represent improved cytotoxicity against LLC-PK, compared to their ansa-analogues.     

Synthesis of double headed imidazoline acyclo C-nucleosides: 1,4-bis[1-amino-5-oxo-4-substituted(imidazolin-2-yl)]galacto-tetritols

Condensation of 2,3,4,5-tetra-O-acetyl-galactaroyl dichloride (1) with two equivalents of the alpha-amino esters 2a-c gave the corresponding 2,3,4,5-tetra-O-acetyl-galactaric acid diamides 3a-c. Heterocyclization of 3a-c by heating with hydrazine hydrate took place with concomitant de-O-acetylation of the polyacetoxyalkyl chain to give 1,4-bis[1-amino-5-oxo-4-substituted(imidazolin-2-yl)] galacto-tetritols (5a-c) and not the theoretically possible 1,2,4-triazinones 4 as indicated by spectral data. Compounds 5a-c readily reacted with p-nitrobenzaldehyde to give the corresponding p-nitrobenzylideneamino derivatives 6a-c. Acetylation of 5a-c afforded the 2,3,4,5-tetra-O-acetyl-1,4-bis[1-acetamido-5-oxo-4-substituted(imidazolin-2-yl)]galacto-tetritols (7a,b,d). De-O-acetylation of 7a,b,d gave 1,4-bis[1-acetamido-5-oxo-4-substituted (imidazolin-2-yl)]galacto-tetritols (8a-c).     

Synthesis and DNA binding studies of novel heterocyclic substituted quinoline schiff bases: a potent antimicrobial agent

The present article deals with the synthesis of 2-chloroquinoline-3-carbaldehyde [(2-hydroxy-1-naphthyl) methylene] hydrazone (CQCMH) (2a-c) and 2-chloroquinoline-3-carbaldehyde [4-(dimethylamino) benzylidene] hydrazone (CQCDBH) (3a-c) from quinoline derivatives under suitable experimental conditions. The synthesized compounds were characterized by elemental analysis, FTIR, (1)HNMR, and mass spectral data. The selected compounds were studied for interaction with calf thymus-DNA (CT-DNA) by electronic spectra, viscosity measurements as well as thermal denaturation studies. On binding to DNA, the absorption spectrum underwent bathochromic and hypochromic shifts. The binding constant (K(b)) had value of 2.3 x 10(3) M(-1) for (2a) and 2.5 x 10(4) M(-1) for (3a). The viscosity measurements indicated that the viscosity of sonicated rod like DNA fragments increased. The synthesized derivatives have been screened for antibacterial and antifungal activities.     

Synthesis of 2-bromomethyl-3-hydroxy-2-hydroxymethyl-propyl pyrimidine and theophylline nucleosides under microwave irradiation. Evaluation of their activity against hepatitis B virus

Alkylation of 2-methylthiopyrimidin-4(1H)-one (1a) and its 5(6)-alkyl derivatives 1b-d as well as theophylline (7) with 2,2-bis(bromomethyl)-1,3-diacetoxypropane (2) under microwave irradiation gave the corresponding acyclonucleosides 1-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]-2-methyl-thio pyrmidin-4(1H)-ones 3a-d and 7-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]theophylline (8), which upon further irradiation gave the double-headed acyclonucleosides 1,1 '-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis[(2-(methylthio)-pyrimidin-4(1H)-ones] 4a-c, and 7,7 '-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis(theophylline) (9). The deacetylated derivatives were obtained by the action of sodium methoxide. The activity of deacetylated nucleosides against Hepatitis B virus was evaluated. Compound 5b showed moderate inhibition activity against HBV with mild cytotoxicity.     

Bis[platinum(II)] and bis[platinum(IV)] complexes with optically active bis(vicinal-1,2-diamines) and their interaction with DNA.

Bis[platinum(II)] [Cl2Pt(LL)PtCl2] complexes 2,5 and 8 with chiral non-racemic ligands: 1a-c (LL = (R,R), (S,S) and (R,S) N,N'-bis(3,4-diaminobutyl)hexanediamide); 4a,b (LL = (R,R) and (S,S) N,N'-bis[3,4-bis(diaminobutyl)] urea); 7a-d (LL' = (R,R), (S,S), (R,S) and (S,R) 4,5-diamino-N-(3,4-diaminobutyl) pentanamide) and bis[platinum(IV)] complex 10-13 with ligands 1a,b and 4a,b have been prepared and characterized by IR, 1H, 13C and 195Pt NMR spectra. The interactions of 2a-c, 5a, 5b, 8a-d and 10a with dsDNA were investigated with the goal of examining whether the chirality, the nature of the spacer and the oxidation state have an influence on platinum-DNA binding properties. All the bis[platinum(II)] complexes form with dsDNA intra- and interstrand crosslinks and crosslinks over sticky ends, whereas the bis[platinum(IV)] complex 10a only forms intra- and interstrand crosslinks. The platinum-DNA coordination sites were determined by the T4 DNA polymerase footprinting method. The results show that all investigated bis(platinum) complexes have high preference towards distinct purines. All isomeric bis(amide) 2a-c and mono(amide) 8a-d complexes exhibit nearly the same binding pattern, whereas the ureide complexes 5a and 5b have other coordination sites with higher sequence preference. Interestingly, the ureides 5a and 5b differ in their coordination sites not only in comparison to the bis(amides) 2a-c and mono(amides) 8a-d, but also between each other. The bis[platinum(IV)] complex 10a also differs in coordination sites in comparison to all the bis[platinum(II)] compounds.     

Structural and mechanistic insight into the inhibition of aspartic proteases by a slow-tight binding inhibitor from an extremophilic Bacillus sp.: correlation of the kinetic parameters with the inhibitor induced conformational changes

We present here the first report of a hydrophilic peptidic inhibitor, ATBI, from an extremophilic Bacillus sp. exhibiting a two-step inhibition mechanism against the aspartic proteases, pepsin and F-prot from Aspergillus saitoi. Kinetic analysis shows that these proteases are competitively inhibited by ATBI. The progress curves are time-dependent and consistent with slow-tight binding inhibition: E + I right arrow over left arrow (k(3), k(4)) EI right arrow over left arrow (k(5), k(6)) EI. The K(i) values for the first reversible complex (EI) of ATBI with pepsin and F-prot were (17 +/- 0.5) x 10(-9) M and (3.2 +/- 0.6) x 10(-6) M, whereas the overall inhibition constant K(i) values were (55 +/- 0.5) x 10(-12) M and (5.2 +/- 0.6) x 10(-8) M, respectively. The rate constant k(5) revealed a faster isomerization of EI for F-prot [(2.3 +/- 0.4) x 10(-3) s(-1)] than pepsin [(7.7 +/- 0.3) x 10(-4) s(-1)]. However, ATBI dissociated from the tight enzyme-inhibitor complex (EI) of F-prot faster [(3.8 +/- 0.5) x 10(-5) s(-1)] than pepsin [(2.5 +/- 0.4) x 10(-6) s(-1)]. Comparative analysis of the kinetic parameters with pepstatin, the known inhibitor of pepsin, revealed a higher value of k(5)/k(6) for ATBI. The binding of the inhibitor with the aspartic proteases and the subsequent conformational changes induced were monitored by exploiting the intrinsic tryptophanyl fluorescence. The rate constants derived from the fluorescence data were in agreement with those obtained from the kinetic analysis; therefore, the induced conformational changes were correlated to the isomerization of EI to EI. Chemical modification of the Asp or Glu by WRK and Lys residues by TNBS abolished the antiproteolytic activity and revealed the involvement of two carboxyl groups and one amine group of ATBI in the enzymatic inactivation.     

Synthesis,structural characterization and in vitro cytotoxicity of organotin(IV) derivatives of heterocyclic thioamides, 2-mercaptobenzothiazole, 5-chloro-2-mercaptobenzothiazole, 3-methyl-2-mercaptobenzothiazole and 2-mercaptonicotinic acid

Five new organotin(IV) molecules with the heterocyclic thioamides; 2-mercaptobenzothiazole (Hmbzt), 5-chloro-2-mercaptobenzothiazole (Hcmbzt), 3-methyl-2-mercaptobenzothiazole (mmbzt) and 2-mercaptonicotinic acid (H(2)mna) of formulae [(n-C(4)H(9))(2)Sn(mbzt)(2)] (1), [(C(6)H(5))(2)Sn(mbzt)(2)] (2), [(CH(3))(2)Sn(cmbzt)(2)].1.7(H(2)O)] (3), [(n-C(4)H(9))(2)SnCl(2)(mmbzt)(2).(CH(2)Cl(2))] (4) and [[(C(6)H(5))(3)Sn](2)(mna).[(CH(3))(2)CO]] (5) have been synthesized and characterized by elemental analysis, 1H-, 13C-NMR, FT-IR and M?ssbauer spectroscopic techniques. Crystal structures of molecules 1, 3 and 5 have been determined by X-ray diffraction at 173(1) K (1 and 5) and 293(2) K (3). Compound 1 C(22)H(26)N(2)S(4)Sn, is monoclinic, space group C2/c, a=44.018(2), b=8.8864(5), c=12.8633(7) A, beta=104.195(5) degrees, Z=8. Compound 3 is also monoclinic, space group P2(1)/c and a=17.128(2) A, b=17.919(2) A, c=7.3580(10) A, beta=98.290(10) degrees, Z=4. In both molecules 1 and 3, two carbon atoms from aryl groups, two sulfur and two nitrogen atoms from thione ligands form a distorted octahedral geometry around tin(IV) with trans-C(2), cis-N(2), cis-S(2) configurations. Compound 5 C(45)H(39)NO(3)SSn(2) is monoclinic, space group P2(1)/n, a=9.1148(2) A, b=29.2819(6), c=15.5556(4) A, beta=106.2851(9) degrees, Z=4. Complex 5 contains two [(C(6)H(5))(3)Sn(IV)] moieties linked by a double deprotonated 2-mercaptonicotinic acid (H(2)mna). Both tin(IV) ions are five coordinated. This complex is the an example of a pentacoordinated Ph(3)SnXY system with an axial-equatorial arrangement of the phenyl groups at Sn(1) atom. Compounds 1, 3 and 5 were tested for in vitro cytotoxicity against the cancer cell line of sarcoma cells (mesenchymal tissue) from the Wistar rat, polycyclic aromatic hydrocarbons (benzo[a]pyrene) carcinogenesis. Compound 5 exhibits strong cytotoxic activity, while complexes 1 and 3 show less cytotoxic activity.     

DNA damage and 2'-deoxyguanosine oxidation induced by S(IV) autoxidation catalyzed by copper(II) tetraglycine complexes: synergistic effect of a second metal ion

S(IV) (SO(2),HSO(3)(-)andSO(3)(2-)) autoxidation catalyzed by Cu(II)/tetraglycine complexes in the presence of DNA or 2'-deoxyguanosine (dGuo) resulted in DNA strand breaks and formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), respectively. Ni(II), Co(II) or Mn(II) (1.0x10(-4)M) complexes had much smaller effects. Cu(II)/tetraglycine (1.0x10(-4)M) in the presence of Ni(II) or Mn(II) (10(-7)-10(-6)M) and S(IV) showed remarkable synergistic effect with these metal ions producing a higher yield of 8-oxodGuo. Oxidation of dGuo and DNA damage were attributed to oxysulfur radicals formed as intermediates in S(IV) autoxidation catalyzed by transition metal ions. SO*(3)(-) and HO* radicals were detected by EPR-spin trapping experiments with DMPO (5,5-dimethyl-1-pyrroline-N-oxide).     

Dimethyl titanocene Y: A valuable precursor for libraries of cytotoxic titanocene derivatives

Reaction of the known titanocene Y 2 with methyl lithium at −15 °C yields bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dimethyl (dimethyl titanocene Y, 3), a hitherto unknown, surprisingly robust titanium (IV) dimethyl species. Dimethyl titanocene Y was utilized in the preparation of several bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dicarboxylates by the reaction with the free carboxylic acids in fair to good yields. Cytotoxicity of all new compounds has been estimated in Hela S3 cells.     

Novel benzyl-substituted N-heterocyclic carbene-silver acetate complexes: synthesis, cytotoxicity and antibacterial studies

From the reaction of 1-methylimidazole (1a), 4,5-dichloro-1H-imidazole (1b(I)) and 1-methylbenzimidazole (1c) with p-cyanobenzyl bromide (2a), non-symmetrically substituted N-heterocyclic carbene (NHC) [(3a-c)] precursors, 5,6-dimethyl-1H-benzimidazole (1d) and 4,5-diphenyl-1H-imidazole (1e) with p-cyanobenzyl bromide (2a) and benzyl bromide (2b), symmetrically substituted N-heterocyclic carbene (NHC) [(3d-f)] precursors were synthesised. These NHC-precursors were then reacted with silver(i) acetate to yield the NHC-silver complexes (1-methyl-3-(4-cyanobenzyl)imidazole-2-ylidene)silver(i)acetate (4a), (4,5-dichloro-1-(4-cyanobenzyl)-3-methyl)imidazole-2-ylidene)silver(i)acetate (4b), (1-methyl-3-(4-cyanobenzyl)benzimidazole-2-ylidene)silver(i)acetate (4c), (1,3-bis(4-cyanobenzyl)5,6-dimethylbenzimidazole-2-ylidene) silver(i) acetate (4d), (1,3-dibenzyl-5,6-dimethylbenzimidazole-2-ylidene) silver(i) acetate (4e) and (1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene) silver(i) acetate (4f) respectively. Three NHC-precursors 3c-e and four NHC-silver complexes 4b and 4d-f were characterised by single crystal X-ray diffraction. Preliminary in vitro antibacterial activity of the NHC-precursors and NHC-silver complexes was investigated against Gram-positive bacteria Staphylococcus aureus, and Gram-negative bacteria Escherichia coli using the qualitative Kirby-Bauer disk-diffusion method. NHC-silver complexes have shown very high antibacterial activity compared to the NHC-precursors. All six NHC-silver complexes were tested for their cytotoxicity through MTT based in vitro tests on the human renal-cancer cell line Caki-1 in order to determine their IC?? values. NHC-silver complexes 4a-f were found to have IC?? values of 6.2 (±1.0), 7.7 (±1.6), 1.2 (±0.6), 10.8 (±1.9), 24.2 (±1.8) and 13.6 (±1.0) μM, respectively. These values represent improved cytotoxicity against Caki-1, most notably for 4c, which is a three times more cytotoxic than cisplatin (IC?? value = 3.3 μM) itself.     

Transition metal half-sandwich complexes as redox mediators to glucose oxidase

Chromium and manganese half-sandwich complexes are evaluated as mediators to glucose oxidase (GOx) since they are of similar size to ferrocene derivatives (sandwich complexes) and contain a single pi-ligand for interaction with the enzyme co-factor. A series of seven amino derivatives of [(eta-C(6)H(6))Cr(CO)(3)] were investigated of which only [[eta-C(6)Me(4)(NH(2))(2)]Cr(CO)(3)] (7), with the lowest oxidation potential of +40 mV (versus SCE), was found to display reversible electrochemistry. Small catalytic currents were recorded in the presence of GOx and glucose when complex (7) was incorporated in a screen-printed carbon electrode. Manganese cyclopentadienyl (Cp) half-sandwich complexes were found to be more effective GOx mediators and comparable in efficacy to ferrocene derivatives. A mediator rate constant k(M) of 2.1 x 10(5)M(-1)s(-1) was determined for the water-soluble complex [(eta-MeC(5)H(4))Mn(NO)(CN)(2)]Na (11) compared to a range of 3 x 10(4) to 8 x 10(6)M(-1)s(-1) previously determined for ferrocenes under the same experimental conditions. beta-Cyclodextrin (beta-cd) was found to be helpful in solubilising hydrophobic complexes such as [(eta-MeC(5)H(4))Mn(NO)(S(2)CNMe(2))] (15) and the neutral oxidised form of [MeCpMn(NO)[(SCCN)(2)]]NEt(4) (14), either directly as an inclusion adduct or in situ during cyclic voltammetry. Screen-printed amperometric electrodes, containing a mediator and GOx immobilised in an organic conducting carbon layer, were useful in assessing the mediation ability of complex (15) where aqueous insolubility precluded any kinetic studies with GOx in solution. This work was briefly extended to other oxidoreductase enzymes apart from GOx. Thus, rotating ring-disk voltammetry demonstrated that the beta-cd complex of compound (15) is also a useful mediator to Horseradish peroxidase (HRP) since it displays an identical catalytic current to the ferrocene ethanolamine derivative (1) used in the MediSense ExacTech and Precision QID blood glucose biosensor electrodes.     

High and low affinity receptors mediate growth effects of gastrin and gastrin-Gly on DLD-1 human colonic carcinoma cells

Gastrin (G17) and N-carboxymethylgastrin (G17-Gly) have been shown to stimulate the growth of colon cancer cells both in vivo and in vitro. The identity of the receptor mediating these effects is controversial. A recent study demonstrated the presence of a low affinity binding site for G17 and G17-Gly on the DLD-1 human colon cancer cell line. The goal of the current study was to further investigate the role of this receptor in mediating the growth-promoting effects of gastrin peptides. Binding of [Leu(15)]G17 and [Leu(15)]G17-Gly to DLD-1 cell membranes in competition with [(3)H]G17-Gly was examined. Binding of [(3)H]cholecystokinin-8 (CCK8) to DLD-1 cell membranes was also assessed. Whole cell binding experiments were carried out using [(125)I-Tyr(12),Leu(15)]G17-Gly. In addition, the ability of [Leu(15)]G17 and [Leu(15)]G17-Gly to stimulate cell growth, as determined by cell counting, was tested. [Leu(15)]G17 and [Leu(15)]G17-Gly competed with [(3)H]G17-Gly at both a high and a low affinity site on DLD-1 membranes. The IC(50) values for [Leu(15)]G17 were 6.0 x 10(-8) M and 6.9 x 10(-6) M while those for [Leu(15)]G17-Gly were 3.2 x 10(-9) M and 4.9 x 10(-6) M. [(3)H]CCK8 did not bind to either site. [Leu(15)]G17-Gly also competed with [(125)I-Tyr(12),Leu(15)]G17-Gly at both a high and a low affinity site on DLD-1 cells with similar affinities as observed with membranes. [Leu(15)]G17 and [Leu(15)]G17-Gly significantly stimulated the growth of DLD-1 cells in a dose-dependent and biphasic manner. The binding profiles of the peptides tested suggest that these sites are different from previously identified wild-type and mutant CCK(1) or CCK(2) receptors.     

Protease nexin II interactions with coagulation factor XIa are contained within the Kunitz protease inhibitor domain of protease nexin II and the factor XIa catalytic domain

Protease nexin II, a platelet-secreted protein containing a Kunitz-type domain, is a potent inhibitor of factor XIa with an inhibition constant of 250-400 pM. The present study examined the protein interactions responsible for this inhibition. The isolated catalytic domain of factor XIa is inhibited by protease nexin II with an inhibition constant of 437 +/- 62 pM, compared to 229 +/- 40 pM for the intact protein. Factor XIa is inhibited by a recombinant Kunitz domain with an inhibition constant of 344 +/- 37 pM versus 422 +/- 33 pM for the catalytic domain. Kinetic rate constants were determined by progress curve analysis. The association rate constants for inhibition of factor XIa by protease nexin II [(3.35 +/- 0.35) x 10(6) M(-1) s(-1)] and catalytic domain [(2.27 +/- 0. 25) x 10(6) M(-1) s(-1)] are nearly identical. The dissociation rate constants are very similar, (9.17 +/- 0.71) x 10(-4) and (7.97 +/- 1.1) x 10(-4) s(-1), respectively. The rate constants for factor XIa and catalytic domain inhibition by recombinant Kunitz domain are also very similar: association constants of (3.19 +/- 0.29) x 10(6) and (3.25 +/- 0.44) x 10(6) M(-1) s(-1), respectively; dissociation constants of (10.73 +/- 0.84) x 10(-4) and (10.36 +/- 1.3) x 10(-4) s(-1). The inhibition constant (K(i)) values calculated from these kinetic parameters are in close agreement with those measured from equilibrium binding experiments. These results suggest that the major interactions required for factor XIa inhibition by protease nexin II are localized to the catalytic domain of factor XIa and the Kunitz domain of protease nexin II.     

Chemical structure and chain conformation of the water-insoluble glucan isolated from Pleurotus tuber-regium

A water-insoluble polysaccharide (TM8) was isolated from sclerotium of Pleurotus tuber-regium by extraction with 0.5M NaOH aqueous solutions at 120 degrees C. Its chemical structure was confirmed by infrared, high performance liquid chromatography, gas chromatography, and (13)C NMR in dimethylsulfoxide (DMSO) to be composed of beta-(1 --> 3)-D-glucan backbone chain linked with a branched glucose, one out of every three glycosyl units being substituted at C6 position. The glucan TM8 in DMSO was fractionated by nonsolvent addition method into ten fractions, and the solution properties were studied by size exclusion chromatography combined with multiangle laser light scattering (SEC-MALLS) and viscometry in DMSO at 30 degrees C. The dependencies of intrinsic viscosity [eta] and radius of gyration [(s(2)(1/2)(z-2)] on weight-average molecular mass M(w) for this glucan were found to be [eta] = (9.24 +/- 0.2) x 10(-2)M(w)(0.51 +/- 0.02) (cm(3)g(-1)) and [(s(2)(1/2)(z-2)] = (3.67 +/- 0.3) x 10(-2)M(w)(0.56 +/- 0.02) (nm) in the range of M(w) from 1.07 x 10(4) to 77.4 x 10(4). Based on current theories for a wormlike chain, the conformational parameters of the glucan TM8 were found to be 408 (nm(-1)) for M(L), 3.1 (nm) for q, and 16.8 for C(infinity), suggesting that the polysaccharide exists as a dense random-coil chain in DMSO, due to branched structure.     

Synthesis and biological evaluation of some acyclic alpha-(1H-pyrazolo-[3,4-d]pyrimidin-4-yl)thioalkylamide nucleosides

The chemical synthesis of some acyclic alpha-(1H-pyrazolo[3,4-d]pyrimidin-4-yl)thioalkylamide nucleosides (10-12)a-c is described. The treatment of IH-pyrazolo[3,4-d]pyrimidin-4-thione 1 with compounds 2a-c gave, regioselectively, ethyl alpha-(1H-pyrazolo[3,4-d]pyrimidin-4-yl)thioalkylates 3a-c, respectively. These heterocycles were alkylated, separately, with alkylating agents 4, 5 and 6 to give, regioselectively, the N1-acyclic nucleosides (7-9)a-c which were deprotected to afford the desired products (10-12)a-c. All synthetic compounds were characterized on the basis of their physical and spectroscopic properties. The products (10-12)a-c were evaluated for their inhibitory effects against the replication of HIV-1 (III(B)), HIV-2 (ROD), various DNA viruses, a variety of tumor-cell lines and M. tuberculosis. No marked biological activity was found.