Stable benzotriazole esters as mechanism-based inactivators of the severe acute respiratory syndrome 3CL protease.

Severe acute respiratory syndrome (SARS) is caused by a newly emerged coronavirus that infected more than 8000 individuals and resulted in more than 800 fatalities in 2003. Currently, there is no effective treatment for this epidemic. SARS-3CL(pro) has been shown to be essential for replication and is thus a target for drug discovery. Here, a class of stable benzotriazole esters was reported as mechanism-based inactivators of 3CL(pro), and the most potent inactivator exhibited a k(inact) of 0.0011 s(-1) and a K(i) of 7.5 nM. Mechanistic investigation with kinetic and mass spectrometry analyses indicates that the active site Cys145 is acylated, and that no irreversible inactivation was observed with the use of the C145A mutant. In addition, a noncovalent, competitive inhibition became apparent by using benzotriazole ester surrogates in which the bridged ester-oxygen group is replaced with carbon.

Design, synthesis, and photodegradation of silicon-containing polyureas.

Novel N-phenyl aromatic polyureas containing bis[(N,N'-diphenylureylene)methyl]silane units in the skeleton were designed as a new type of photodegradable polymer. These materials were successfully prepared in 88-93 % yields by copolymerization of bis(anilinomethyl)dimethylsilane and dianilino-p-xylene with 4,4'-methylenebis(phenylisocyanate). Their photodegradability was found to be 10.1 times higher than that of polymers of similar structure, but lacking the silyl unit. Furthermore, the photodegradation mechanism of polyureas was elucidated, and involves single-electron transfer between silyl and carbonyl groups, silyl group migration, and solvolysis. These novel polymers are potential materials of high economic value for use in photolithography and microelectronics.

Aminyl and iminyl radicals from arylhydrazones in the photo-induced DNA cleavage.

Photolytic cleavage of the nitrogen-nitrogen single bond in benzaldehyde phenylhydrazones produced aminyl (R2N*) and iminyl (R2C=N*) radicals. This photochemical property was utilized in the development of hydrazones as photo-induced DNA-cleaving agents. Irradiation with 350 nm UV light of arylhydrazones bearing substituents of various types in a phosphate buffer solution containing the supercoiled circular phiX174 RFI DNA at pH 6.0 resulted in single-strand cleavage of DNA. Attachment of the electron-donating OMe group to arylhydrazones increased their DNA-cleaving activity. Results from systematic studies indicate that both the aminyl and the iminyl radicals possessed DNA-cleaving ability.

Novel antiviral agent tetraglycylated nordihydroguaiaretic acid hydrochloride as a host-dependent viral inhibitor.

A water soluble derivative of nordihydroguaiaretic acid (NDGA), G(4)N (2), synthesized by reaction of NDGA (1) with N,N-dimethylglycine in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine and then with HCl(g) (Scheme 1), competes effectively with the DNA binding domain of recombinant Sp1 protein for binding to the human immunodeficiency virus (HIV) LTR as demonstrated by an electrophoretic mobility-shift assay (EMSA). By blocking Sp1 binding to the HIV LTR, G(4)N suppresses Sp1-regulated HIV Tat transactivation and replication in cultured cells with an IC(50) of 12 microM similar to that of 3'-O-methyl-NDGA as we have previously reported. In addition simian immunodeficiency virus (SIV) replication was completely inhibited by G(4)N at 5.0 microM. G(4)N showed no toxic effect to 174 x CEM cells and H9 cells at 100 microM.

Synthesis and immunofluorescence assay of a new biotinylated paclitaxel.

7-(5'-Biotinylamidopropanoyl)paclitaxel was synthesised by chemical methods; its immunofluorescence assay and the cell uptake experiments were performed by use of human leukemia U937 cells. The results indicate that paclitaxel is arresting cell cycle at the G(2)M phase only.