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- Denmeade, Samuel R., et al.
(författare)
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Specific and efficient peptide substrates for assaying the proteolytic activity of prostate-specific antigen
- 1997
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Ingår i: Cancer Research. - 0008-5472. ; 57:21, s. 4924-4930
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Tidskriftsartikel (refereegranskat)abstract
- Prostate-specific antigen (PSA) is a serine protease secreted by hath normal prostate glandular celts and prostate cancer cells. The major proteolytic substrates for PSA are the gel-forming proteins in semen, semenogelin (Sg) I and II. On the basis of the PSA cleavage map for Sg I and II, a series of small peptides (ie., ≤ 7 amino acids) was synthesized and coupled at the COOH terminus to 7-amino-4-methyl coumarin. Using these fluorescently tagged substrates, K(m)s and k(cm)s were determined for PSA hydrolysis, and the substrates were also tested for activity against a panel of purified proteases. Previously, a variety of chymotrypsin substrates have been used to assay the enzymatic activity of PSA. The present studies have identified a peptide sequence with a high degree of specificity for PSA (i.e., no detectable hydrolysis by chymotrypsin) and improved K(m)s and k(cat)s over previously used substrates. On the basis of these parameters, the best peptide substrate for PSA has the amino acid sequence HSSKLQ. Using PC-82 human prostate cancer xenografts and human prostate tissues, this PSA substrate was used to document that prostate cancer cells secrete enzymatically active PSA into the extracellular fluid but that once in the blood, PSA is not enzymatically active. On the basis of this information, it should be possible to use the HSSKLQ peptide as a carrier to target peptide- coupled prodrugs for selective activation within sites of PSA-secreting, metastatic prostate cancer cells and not within the blood or other nonprostatic normal tissues.
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| 2. |
- Gao, Ming-Wei, et al.
(författare)
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Power predictions for a pilot scale stirred ball mill
- 1996
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Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 44-45, s. 641-652
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of a stirred ball mill to grind to a certain product size efficiently depends strongly on the power intensity in the milling chamber. The dependence of power intensity on stirrer speed, slurry density, bead density and the amount of dispersant added to the feed was investigated using a 6-litre 11-kW horizontal stirred ball mill fitted with perforated disks as stirrers. Dolomite was ground at a fixed volumetric flow rate, but with slurry densities ranging from 65 to 75 percent by weight, stirrer speeds from 805 to 2253 rpm, bead densities from 2.5 to 5.4 g/ml and the dispersant level from 0.5 to 1.5 percent of dry solids. Three levels of the four variables were used in 27 continuous milling tests, set up as one-third of a 34 factorial design. All factors affected the power draft in a highly significant way. Speed, and to a lesser extent slurry density, were the dominant factors with significant non-linear effects. A six-term model, incorporating all significant effects, predicted the experimental results with an accuracy of about 12%. Increasing the power accelerated size reduction dramatically with only a small change to the energy efficiency of the process.
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| 5. |
- Wei, T, et al.
(författare)
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Interaction of the IciA protein with AT-rich regions in plasmid replication origins
- 1996
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Ingår i: NUCLEIC ACIDS RESEARCH. - : OXFORD UNIV PRESS UNITED KINGDOM. - 0305-1048. ; 24:10, s. 1865-1872
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A set of AT-rich repeats is a common motif in prokaryotic replication origins, We have screened for proteins binding to the AT-rich repeat region in plasmids F, R1 and pSC101 using an electrophoretic mobility shift assay with PCR-amplified DNA fragments f
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