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Biomedical subjects

J Hajdu

Publications and source records attributed to J Hajdu.

118 records · Page 7Linked to original sources
PubMed1975

Cross-linking and coupling of rabbit muscle aldolase and glyceraldehyde-3-phosphate dehydrogenase by glutaraldehyde.

The mode of cross-linking of rabbit-muscle aldolase and glyceraldehyde-3-phosphate dehydrogenase by glutaraldehyde was studied. The about 5 A long reagent can partly cross-link subunits within the tetramers, whereas it is readily able to make intermolecular cross-links producing polymeric enzyme species. Of the two enzymes, glyceraldehyde-3-phosphate dehydrogenase has a greater tendency to polymerize in the presence of glutaraldehyde. In the case of aldolase, the inter- and intramolecular cross-links between subunits can be distinguished by SDS gel-electrophoresis. The copolymerization pattern of the two enzymes indicates that, though the formation of mixed polyenzymes can be detected by affinity chromatography on human erythrocyte ghosts, under the conditions tested these proteins do not form heterologous enzyme complexes that could be trapped by glutaraldehyde.

Aldehydes↗
PubMedDate not supplied

A two-step purification procedure for sheep liver 6-phosphogluconate dehydrogenase.

A two-step procedure for the purification of 6-phosphogluconate dehydrogenase (EC 1.1.1.44; 6-PGDH) from sheep liver is described. The enzyme is directly bound to cellulose phosphate by batch extraction and eluted with a linear salt gradient. Purification is completed by affinity chromatography using NADP(+)-agarose. The result is 6-PGDH of high purity, greatly increased yield, and the highest specific activity yet achieved, with a significant reduction in the purification time.

Animals↗
PubMedDate not supplied

Diffraction imaging of single particles and biomolecules.

Theory predicts that with a very short and very intense X-ray pulse, the image of a single diffraction pattern may be recorded from a large macromolecule, a virus, or a nanocluster of proteins without the need for a crystal. A three-dimensional data set can be assembled from such images when many copies of the molecule are exposed to the beam one by one in random orientations. We outline a method for structure reconstruction from such a data set in which no independent information is available about the orientation of the images. The basic requirement for reconstruction and/or signal averaging is the ability to tell whether two noisy diffraction patterns represent the same view of the sample or two different views. With this knowledge, averaging techniques can be used to enhance the signal and extend the resolution in a redundant data set. Based on statistical properties of the diffraction pattern, we present an analytical solution to the classification problem. The solution connects the number of incident X-ray photons with the particle size and the achievable resolution. The results are surprising in that they show that classification can be done with less than one photon per pixel in the limiting resolution shell, assuming Poisson-type photon noise in the image. The results can also be used to provide criteria for improvements in other image classification procedures, e.g., those used in electron tomography or diffraction.

Electrons↗
PubMedDate not supplied

Millisecond X-ray diffraction and the first electron density map from Laue photographs of a protein crystal.

Attempts to use X-ray crystallography to extract three-dimensional information on transient phenomena in crystals have been hampered primarily by long data collection times. Here we report on the first difference Fourier map obtained from Laue diffraction photographs of a protein crystal, glycogen phosphorylase b. Data collection time was 3 s using the high-intensity white X-radiation generated on the wiggler magnet of the Daresbury Synchrotron Radiation Source (SRS), but data acquisition in the millisecond-submillisecond range is possible. The method presented here uses a simple difference technique and was designed to analyse structural changes relative to a known starting structure. The combination of this approach with cine techniques allows the recording of three-dimensional motion pictures at atomic resolution and opens up new areas in structural biology and chemistry.

Electrons↗
PubMedDate not supplied

Copy number of cancer genes predict tumor grade and survival of pancreatic cancer patients.

Pancreatic cancer is on the increase. While means of early diagnosis are being sought, it continues to present late. Prognostication is based on patient and tumor characteristics, including expression or mutation of cancer-related genes. Few studies have examined the impact of the amplification of these genes on the outcome of pancreatic cancer. We have now used a non-radioisotopic slot-blot technique to relate gene copy numbers of p53, c-myc and K-ras to tumor grade and survival. Outcomes were corrected for patient characteristics, tumor location and TNM staging. The Kaplan-Meier test for likelihood of survival showed that increase in copy number of the two oncogenes and loss of p53 were associated with non-significant reduction in survival. When these variations in cancer gene copy numbers were, however, examined by logistic regression analysis in the context of patient and tumor characteristics, survival was negatively related to K-ras amplification (p = 0.0291). Tumor grade, but not survival was positively related to loss of p53 gene copy (p = 0.0131) as well as c-myc amplification (p = 0.0248). Thus using a simple non-radioisotopic technique for the detection of cancer gene copy number in association with patients and disease characteristics, we could predict survival on the one hand and tumor behavior on the other. Such information could be used to plan initial and follow-up therapy.

Adult↗