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S T Liu

Publications and source records attributed to S T Liu.

82 records · Page 5Linked to original sources
PubMed1981

Rapid procedure for detection and isolation of large and small plasmids.

Procedures are described for the detection and isolation of plasmids of various sizes (2.6 to 350 megadaltons) that are harbored in species of Agrobacterium, Rhizobium, Escherichia, Salmonella, Erwinia, Pseudomonas, and Xanthomonas. The method utilized the molecular characteristics of covalently closed circular deoxyribonucleic acid (DNA) that is released from cells under conditions that denature chromosomal DNA by using alkaline sodium dodecyl sulfate (pH 12.6) at elevated temperatures. Proteins and cell debris were removed by extraction with phenol-chloroform. Under these conditions chromosomal DNA concentrations were reduced or eliminated. The clarified extract was used directly for electrophoretic analysis. These procedures also permitted the selective isolation of plasmid DNA that can be used directly in nick translation, restriction endonuclease analysis, transformation, and DNA cloning experiments.

Bacteriological Techniques↗
PubMed1978

Effect of enantiomeric purity on solubility determination of dexclamol hydrochloride.

The solubility of (+/-)-4a,13b-trans)-[3(OH),13b(H)-trans]-3-isopropyl - 2,3,4,4a,8,9,13b,14- octahydro-1H - benzo[6,7]cycloheptal[1,2,3-de]pyrido[2,1-a]isoquinolin-3-ol hydrochloride [(+/-)-I] was 3.3 mg/ml in pure water. Its resolved enantiomers exhibited about a fivefold increase in solubility. Dexclamol hydrochloride, the (+)-I enantiomer, is bioactive as a neuroleptic and is soluble to the extent of 16.4 mg/ml. However, raw material purity in relation to the amounts of (+/-)-I racemate present significantly influences solubility and optimum conditions for dissolution. The effect of trace amounts of (-)-I or (+/-)-I forms of the solubility of (+)-I enantiomer raw materials was explained through phase solubility studies. Conditions required for preparation of clear solutions using raw materials of varying purity can be determined with derived expressions. The application and limitations of using an enantiomer as a tool to improve solubility are discussed.

Dibenzocycloheptenes↗
PubMed1978

Bound Form Indole-3-acetic Acid Synthesis in Tumorous and Nontumorous Species of Nicotiana.

The synthesis of H(2)O-soluble and NaOH-hydrolyzable bound forms of indole-3-acetic acid (IAA) in petiole slices of Nicotiana glauca, Nicotiana langsdorffii, and their tumorous and nontumorous hybrids in the presence of exogenous (14)C-IAA was investigated. The synthesis of conjugates progressively increased during 6 hours of incubation in (14)C-IAA. The results showed that the rate of synthesis of IAA conjugates was higher in tumorous hybrids supplied exogenous IAA than in the parental species similarly supplied, and the rate of synthesis was higher in amphidiploid tumor plants than in a nontumorous mutant. It was also found that after 10 to 12 hours of incubation, 45% of the IAA taken up by F1 hybrids was in conjugated form whereas only 10 to 25% of the IAA taken up by a nontumorous mutant, N. langsdorffii, or N. glauca was conjugated. An F1 hybrid and an amphidiploid hybrid were found equally efficient in conjugating exogenously supplied IAA. It is postulated on the basis of these and other findings that IAA conjugates play an important role in tumorigenesis in Nicotiana.

Journal Article↗
PubMed1978

Indole-3-acetic Acid Synthesis in Tumorous and Nontumorous Species of Nicotiana.

The synthesis of indole-3-acetic acid (IAA) in the enzyme extracts of Nicotiana glauca, Nicotiana langsdorffii, their F1 hybrid, their amphidiploid hybrid, and the nontumorous mutant of the hybrid was investigated. Tryptamine, a possible precursor of IAA biosynthesis in Nicotiana tabacum, was not found in the callus tissue of N. glauca, N. langsdorffii, and their F1 hybrid.In petiole slices, the synthesis of IAA progressively increased during 5 hours of incubation in [(14)C]tryptophan. The rate of synthesis was about equal in the hybrid and N. langsdorffii but lower in N. glauca on either a cell or fresh weight basis. It was also found that tryptophan was about 25 times more efficient than tryptamine in promoting synthesis of IAA in petiole slices.It was found that indoleacetaldehyde oxidase, indoleacetaldehyde reductase, and tryptophan aminotransferase activities were present in all of the species examined; however, tryptophan decarboxylase activity was not found. The tryptophan aminotransferase activity in N. glauca, N. langsdorffii, and the nontumorous mutant required alpha-ketoglutaric acid and pyridoxal 5-phosphate whereas the addition of pyridoxal 5-phosphate seemed not to increase the enzyme activity in tumor plants.The tryptophan aminotransferase in the amphidiploid hybrid was partially purified by acetone precipitation. The enzyme activity had a temperature optimum at 49 C and a pH optimum at 8.9. It is suggested that there is an indolepyruvic acid pathway in the synthesis of IAA in the Nicotiana species examined.

Journal Article↗
PubMed1977

Determination of aqueous solubility and pKa values of estrogens.

Reported estrone pKa and solubility data show wide variation. Improved experimental procedures were designed and used to obtain reproducible results. The pKa values for several estrogens and related compounds also were determined to assess the effects of structural differences on ionization. No evidence was obtained for long-range D to A ring electronic transmission affecting pKa. Significant differences in pKa values resulted only when conjugated unsaturation was added into the B ring of estrone or estradiol. The aqueous solubilities of estrone and 17alpha-estradiol were 0.8 and 3.9 microgram/ml, respectively, at 25degrees.

Chemical Phenomena↗
PubMedDate not supplied

Rapid detection of hog cholera virus in tissues by the polymerase chain reaction.

A rapid method for the detection of hog cholera virus (HCV) in infected tissues, using polymerase chain reaction (PCR) was developed. Total RNA isolated from HCV-infected tissues was reverse transcribed with AMV reverse transcriptase and the resulting complementary DNA was amplified by Taq DNA polymerase in the presence of two HCV-specific primers. The amplified DNA fragment was detected by agarose gel electrophoresis. The sensitivity of this method was at 10(4) TCID50 of HCV. The sensitivity increased approximately 1000-fold when the DNA was reamplified with a set of nested primers. DNA sequencing analysis of the PCR products revealed that the HCV sequence amplified from a local field isolate was highly homologous to the HCV Alfort strain. This method may be useful for pathological and epidemiological studies of HCV in pigs.

Animals↗
PubMedDate not supplied

Targeting the kinetochore for mitosis-specific inhibitors.

Microtubule poisons such as taxol and vinblastine are widely used to treat a variety of cancers. These drugs are believed to kill cells by blocking mitosis. However, there is a critical need to identify new drugs because tumors can often become refractory to treatment with existing drugs. Studies over the past decade on chromosome segregation have uncovered a plethora of novel proteins that function specifically in mitosis. Centrosomes and kinetochores are two organelles that specify formation of the spindle and the attachment of chromosomes to the spindle, respectively. The focus of this review is to highlight the kinetochore as a rich source of targets for the development of mitosis-specific drugs.

Animals↗