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X C Zhan

Publications and source records attributed to X C Zhan.

8 recordsLinked to original sources
PubMed1997

[Determination of rate order for degradation of drugs with nonisothermal stability experiment].

By a theoretical investigation of simulated nonisothermal data, the inability to determine the rate order for degradation of drugs with ordinary nonisothermal experiment was discussed. Results indicate that both rate order n and activation energy E can change the curvature of the c-t curve and the change caused by higher n can be compensated by higher E in ordinary nonisothermal experiments. That means a suitable E can always be assessed to fit each of the definite n (0, 1, or 2 in our study) very well. As a result, a same set of c-t data can be well fitted by different combinations of n and E. This is why the rate order cannot be assessed in ordinary nonisothermal experiments. To overcome this deficiency, it is important that there have both temperature rising and lowering parts in one nonisothermal experiment. A new heating model, temperature rising and lowering program, was presented. With this new heating model, the kinetic parameters, including the rate order, can be obtained in one nonisothermal stability experiment. The ability of the new heating model to determine rate order is almost the same as that of isothermal experiments.

Drug Stability↗
PubMed1995

[Study on shelf-life prediction of drugs under indoor natural light irradiation].

The photodegradation of drugs under natural light and various lamp light irradiation was studied and the shelf-life of drugs under indoor natural light irradiation was predicted with hydroxyprogesterone caproate injection as an example. The equivalent influences of different light sources on the photostability of the above drug were obtained. Therefore, the natural light photostability and the shelf-life of drugs under indoor natural light irradiation can be studied with lamp light exposure experiment. The photodegradation of hydroxyprogesterone caproate injection obeys zero order kinetics: C = C0-kEt, and its shelf-life under indoor natural light irradiation is about 1.9 years.

17 alpha-Hydroxyprogesterone Caproate↗
PubMed1992

[Obtaining natural light photostability of drugs from lamp light exposure experiments].

The photostability of vitamin B2, vitamin K3, zinc sulfadiazine and vesnarinone, and the equivalent influences of different light sources on the photostability of the above drugs were studied under natural light and lamp lights. From this study, the photostability of drugs under different light sources can be converted to each other, and the natural light photostability of drugs can be conveniently obtained from lamp light exposure experiments. The relationship between the surface reflectance of the above drugs and the cumulative illumination of different light sources can be formulated as R = A + B(Et) + C/(Et + D) accurately, and the cumulative illumination of different light sources irradiated on the above drugs can be converted to each other equivalently.

Drug Stability↗
PubMed1991

Analysis of the potential promoter sequences of African cassava mosaic virus by transient expression of the beta-glucuronidase gene.

DNA fragments from promoter regions of the geminivirus, African cassava mosaic virus, were cloned into pG1, a vector based on pUC18, producing transcriptional fusions with the beta-glucuronidase (GUS) gene and nopaline synthase termination sequence. The activity of each promoter construct was assessed by analysing the transient expression of GUS in Nicotiana clevelandii protoplasts. The results demonstrated that constructs containing the common region of DNA A showed much stronger promoter activity in the complementary sense than in the viral sense. These results were supported by the analysis of promoter activity in transgenic N. benthamiana plants. In comparison, in protoplasts a region upstream of the AC2 open reading frame was shown to have moderate promoter activity. Unlike DNA A, the complementary sense DNA B promoter constructs had weak activity; the viral sense DNA B promoter constructs appeared to be regulated by host factors. The implications of these results for the regulation of early and late genes are discussed.

Base Sequence↗
PubMed1991

Mutagenesis of the AC3 open reading frame of African cassava mosaic virus DNA A reduces DNA B replication and ameliorates disease symptoms.

Small insertions were made independently at each of four unique restriction sites on African cassava mosaic virus (ACMV) DNA A to disrupt the three overlapping complementary-sense open reading frames (ORFs) herein designated AC1, AC2 and AC3. The DNA A mutants were assayed for their infectivity by agroinoculation of monomeric constructs to Nicotiana benthamiana plants containing chromosomal insertions of ACMV DNA B. Disruption of the AC3 ORF alone resulted in a delay and amelioration of disease symptoms which correlated with reduced replication of DNA B. Normal replication of DNA A still carrying the AC3 ORF mutation was found in extracts from these plants. No ACMV DNA or symptoms were observed in corresponding inoculations with either the simultaneous disruption of the overlapping AC2 and AC3 ORFs or disruption of the AC1 ORF. Complementation by the inoculation of different mutant pairs produced a delay in disease symptoms followed by repair of mutated sites. A DNA A construct with the virus-sense AV1 (coat protein) ORF deleted was infectious producing typical ACMV disease symptoms. A similar construct with a larger deletion encompassing the complementary-sense AC3 ORF produced symptomless infections. The DNA recovered from plants revealed DNA A of normal size where the position of the deleted ORF was replaced with cloning vector DNA. Significantly reduced DNA B replication was observed for the AC3 deletion construct.

Blotting, Southern↗
PubMed1990

The pTiC58 tzs gene promotes high-efficiency root induction by agropine strain 1855 of Agrobacterium rhizogenes.

Root induction on flax (Linum usitatissimum L.) cotyledon explants by Agrobacterium rhizogenes strain 1855 is markedly increased by co-inoculation with disarmed A. tumefaciens strain LBA 4404 containing a plasmid carrying the tzs gene of pTiC58. Most of the roots (estimated to be more than 90%) were transformed. This effect is most likely due to the secretion of trans-zeatin by A. tumefaciens stimulating the division of plant cells making them more receptive to transformation by A. rhizogenes, although other explanations are possible. This observation supports the idea that the tzs gene, although not essential for transformation, may promote transformation. An obvious application for genetic engineering experiments involving transformation by A. rhizogenes, is to include a vir-induced tzs gene in the transformation system to help maximize transformation efficiency.

DNA, Bacterial↗
PubMed1990

[Photodecomposition of artificial calculus bovis].

Artificial calculus bovis (ACB) is widely used in dispensing Chinese Traditional Patent Medicine as a substitute for Calculus bovis. Photodecomposition rule of ACB sample irradiated with three different light sources was studied by diffuse reflectance spectrophotometry (DRS) in this paper. The results show that, the photodecomposition rate curves of the ACB sample irradiated by all three light sources are composed of two straight lines of different slopes, indicating that they are of two-step apparent first order reaction, the apparent photodecomposition constants in the first steps are about twice as high as those in the second steps. The ACB sample has the fastest photodecomposition rate when irradiated with the UV mercury-arc lamp and the second with the fluorescent mercury-arc lamp and slowest with the iodine-tungsten lamp. In these three light sources apparent photodecomposition constants of ACB sample are respectively: K1, 2.7629 x 10(-5), 4.4132 x 10(-6); k2, 1.2176 x 10(-5), 2.0684 x 10(-6), 1.4357 x 10(-6) (lx-1.h-1). The apparent constants are independent of the product of the radiation intensity and the irradiation time, but the irradiation time is in inverse ratio of the radiation intensity to get the same proportion of the sample photodecomposition. The fading time of the ACB sample under different radiation intensity can be predicted with the kinetic equations reported. The fading time of ACB sample if directly exposed to light in bright room is 1.6 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilirubin↗