PubMed Health⌕ Search

Biomedical subjects

L Zhong

Publications and source records attributed to L Zhong.

119 records · Page 7Linked to original sources
PubMed1994

[Isolation and sequencing of glucoamylase gene from a glucoamylase over producing strain].

Chromosomal DNA was isolated from the mycelia of Aspergillus niger T21, a strain producing glucoamylase at a high level. Southern blot analysis indicated that the glucoamylase gene is situated on a 2.5kb EcoR I -EcoR V fragment. Chromosomal DNA was digested completely with EcoR I, EcoR V. The fragments in the range of 2.0-3.0kb were isolated through electrophoresis in agarose gel. The pooled fragments were ligated onto pBR322 vector prior to transformation into E. coli DH5. Four glucoamylase-specific recombinants were screened by in situ hybridization from the transformants. Restriction mapping and sequencing for one of the four were performed. Data show that the glucoamylase gene from A. niger T21 is a 2.3kb fragment containing four intervening sequences in the coding region.

Aspergillus niger↗
PubMed1993

Synthesis, cloning and sequencing of glucoamylase cDNA from Aspergillus niger mutant T21.

Poly(A)+ RNA was isolated from Aspergillus niger T21, a glucoamylase overproducing strain and was used as template to synthesize double stranded cDNA. A cDNA library was then constructed. The E. coli transformants were screened for the glucoamylase cDNA by in situ colony hybridization with P-labeled fragment of glucoamylase gene as probe. The positive rate was 1.6%. Restriction analysis proved that 32% of the positive clones carried the inserts of 2.1 kb of full length glucoamylase cDNA. Sequence of the glucoamylase cDNA was determined and the result showed that the sequence of glucoamylase gene of the mutant T21 was almost the same as that reported previously. The high rate of glucoamylase cDNA-containing clones in the cDNA library of strain T21 provided evidence of high steady state level of glucoamylase mRNA in mycelium of mutant T21. Most likely it is one of the major causes for the high glucoamylase productivity of mutant T21.

Aspergillus niger↗
PubMed1992

Environment affects amino acid preference for secondary structure.

Three equivocal amino acid sequences were synthesized that are predicted to be alpha-helical from amino acid preference but are found to be primarily beta-strand from x-ray diffraction of their respective proteins. In some solvent systems we recover the alpha-helical structure predicted by amino acid preference, whereas in other systems we mimic the interior of the protein and produce a beta-strand. These results are experimental proof that the environment is important in determining the secondary structure formed by an amino acid sequence; therefore schemes that predict secondary structure from amino acid sequence alone can never be totally successful.

Amino Acid Sequence↗
PubMed1992

Miniature urea sensor based on H(+)-ion sensitive field effect transistor and its application in clinical analysis.

An urea-ENFET (Enzyme field effect transistor) probe was made by covering one of the grids of the dual ISFET (Ion sensitive field effect transistor) with a membrane of cross-linked bovine serum albumin (BSA)-urease and the other with cross-linked BSA, and the response characteristics of the probe was then tested through differential measurements. In different concentrations of phosphate buffer, the sensor responded to various concentrations of urea solution within 10-60s. From the calibration curve plotted on logarithmic scales a linear concentration range of 1.0-8.0 mg/dl was acquired, and the correlation coefficient and response sensitivity were 0.997 and 50mV/dec. (mg/dl), respectively. However, in dilute urea solution, the sensor responded linearly to the contents of urea over the range of concentration of 0.1-1.0 mg/dl with a correlation coefficient of 0.998 and a response sensitivity of 12-15mV/mg/dl. The standard deviation and the variation coefficient for 20 performances responding to 100mg/dl urea in 0.01M pH7.0 phosphate buffer were found to be 1.39mV and 1.44%, respectively. The urea-ENFET was used for the determination of BUN (Blood urea nitrogen) and the BUN values were compared with those determined by enzymatic method, the repression equation and correlation coefficient for 50 assays were y = -0.1272 + 0.9695x and r = 0.9912, respectively. When the urea-ENFET was used for determining urea either in buffer solution or in serum for 250 runs over a period of 1.5 months (the enzyme FET was stored at 4 degrees C between measurements during this period), the observed decrease of response sensitivity was only about 10%.(ABSTRACT TRUNCATED AT 250 WORDS)

Biosensing Techniques↗
PubMed1991

[Investigation on high risk factors of neonatal necrotizing enterocolitis].

In order to evaluate the factors in high-risk neonatal necrotizing enterocolitis (NEC) and predict the prognosis of NEC, a retrospective analysis of 32 factors was made in 42 neonates with NEC. The cases were divided into a low-risk (survival) group and a high-risk (death) group. Of 32 factors compared between these two group, eight were found to be of significance in evaluating the severity of NEC, and six of them were used in the development of a NEC scores (1) number of days before beginning of artificial feeding; (2) neonatal asphyxia or distress; (3) immature form in WBC differential; (4) CO2 combining power; (5) abdominal tenderness; (6) presence of portal vein air (PVA). All laboratory values and physical and radiographic signs were collected during initial presentation of NEC. Neonates with a score of 3 or more are at an increased risk of developing severe NEC with a 83% mortality.

China↗
PubMed1990

[Various methods for purification of urine Tamm-Horsfall protein].

The measurements of serum, urine Tamm-Horsfall protein (THP) and its antibody are essential to the early diagnosis of tubulointerstitial diseases and acute rejection after renal transplantation. The purification of THP proves to be the key procedure for the production of diagnostic kit. Once, twice and three times salt precipitation with 0.58 mol/L NaCl and chromatography with Sephadax G-200 were adopted to purify urine THP. Enzyme immunoassay was used to detect the antigenicity of the products, SDS-PAGE to determine the molecular weight (MW) and the electrophoretic purity (EP), Beckman DU-7 model spectrophotometer to scan the ultraviolet absorption spectrum. Evaluation of the four methods was based on the purity and the antigenicity of the produced THP, the output, the complexity of procedure, and the cost of required materials. Results show that the MW of THP is 93.0 kd; the ultraviolet absorption maximum is at lambda = 278 nm; the outputs are 7.5, 5.5, 3.8, and 0.4 mg/L; the concentrations of THP with antigenicity are 65%, 75%, 98% and 100%, respectively, and the EPs of three times salt precipitation and chromatography are better. It is concluded that three times salt precipitation should be recommended because of its excellence in purity and antigenicity of the produced THP, the simplicity of manipulation, and the cheapness of the materials needed.

Humans↗
PubMedDate not supplied

Serodiagnosis of Asian leishmaniasis with a recombinant antigen from the repetitive domain of a Leishmania kinesin.

rK39 is a recombinant product of the 39 amino acid repeats found in a kinesin-like gene of visceral Leishmania spp. This and other antigens were compared for immunodiagnostic potential by enzyme-linked immunosorbent assay with sera from confirmed cases of Asian cutaneous and visceral leishmaniasis. In preliminary trials, rK39 proved superior to 2 purified Leishmania antigens, a cytosolic protein (p36) and a membrane protein (gp63), for immunodiagnosis of visceral leishmaniasis. Of the 53 visceral cases from China and Pakistan assayed, 52 were seropositive (98%) at a 10(-1) dilution with 36 ng of rK39. End point titrations of 27 highly positive samples yielded anti-rK39 antibody titres ranging from c. 10(-3) to beyond 10(-4). Antigen titrations with one positive serum further revealed that rK39 was 25-fold more sensitive than Leishmania whole cell soluble lysates. 31 cutaneous leishmaniasis cases from Turkey assayed for anti-rK39 antibody gave reactions ranging from negative or marginally positive to positive. In Brazil, all cutaneous and mucocutaneous leishmaniasis cases gave negative results in this assay.

Amino Acid Sequence↗