Structural study of crystalline auromomycin: Preliminary X-ray diffraction study of auromomycin and macromomycin

Auromomycin and macromomycin from the organism Streptomyces macromomyceticus have been crystallized. The X-ray diffraction pattern of crystals of each molecule is consistent with space group P2₁2₁2 with cell parameters $\text{a = 46.45}\text{A}\text{?}\text{, b = 54.34}\text{A}\text{?}\text{and}\text{c = 42.03}\text{A}\text{?}$ for auromomycin, and $\text{a = 46.45}\text{A}\text{?}\text{, b = 54.52}\text{A}\text{?}\text{and}\text{c = 41.54}\text{A}\text{?}$ for macromomycin. Diffraction analysis of auromomycin is in progress.     

SIMS microscopy in the biomedical field.

We attempted to indicate the requirements for biomedical applications of SIMS microscopy. Sample preparation methodology should preserve both the structural and the chemical integrity of the tissue. Furthermore, it is often necessary to correlate ionic and light microscope images. This implies a common methodological approach to sample preparation for both microscopes. The use of low or high mass resolution depends on the elements studied and their concentrations. To improve the acquisition and processing of images, digital imaging systems have to be designed and require both ionic and optical image superimposition. However, the images do not accurately reflect element concentration; a relative quantitative approach is possible by measuring secondary ion beam intensity. Using an internal reference element (carbon) and standard curves the results are expressed in micrograms/mg of tissue. Despite their limited lateral resolution (0.5 microns) the actual SIMS microscopes are very suitable for the resolution of biomedical problems posed by action modes and drug localization in human pathology. SIMS microscopy should provide a new tool for metabolic radiotherapy by facilitating dose evaluation. The advent of high lateral resolution SIMS imaging (less than 0.1 microns) should open up new fields in biomedical investigation.     

Pulsatile flow of Casson's fluid through stenosed arteries with applications to blood flow

The effects of non-Newtonian nature of blood and pulsatility on flow through a stenosed tube have been investigated. A perturbation method is used to analyse the flow. It is of interest to note that the thickness of the viscous flow region is non-uniform (changing with axial distance). An analytic relation between viscous flow region thickness and red cell concentration has been obtained. It is important to mention that some researchers have obtained an approximate solution for the flow rate-pressure gradient equation (assuming the ratio between the yield stress and the wall shear to be very small in comparison to unity); in the present analysis, we have obtained an exact solution for this non-linear equation without making that assumption. The approximate and exact solutions compare well with one of the exact solutions. Another important result is that the mean and steady flow rates decrease as the yield stress theta increases. For the low values of the yield stress, the mean flow rate is higher than the steady flow rate, but for high values of the yield stress, the mean flow rate behaviour is of opposite nature. The critical value of the yield stress at which the flow rate behaviour changes from one type to another has been determined. Further, it seems that there exists a value of the yield stress at which flow stops for both the flows (steady and pulsatile). It is observed that the flow stop yield value for pulsatile flow is lower than the steady flow. The most notable result of pulsatility is the phase lag between the pressure gradient and flow rate, which is further influenced by the yield stress and stenosis. Another important result of pulsatility is the mean resistance to flow is greater than its steady flow value, whereas the mean value of the wall shear for pulsatile flow is equal to steady wall shear. Many standard results regarding Casson and Newtonian fluids flow, uniform tube flow and steady flow can be obtained as the special cases of the present analysis. Finally, some applications of this theoretical analysis have been cited.     

Physicochemical and biological properties of glycoproteins isolated from the plasma of different species of animals

1. Glycoproteins were isolated from the plasma of sheep, goat, cow, buffalo and monkey. They were homogeneous by electrophoresis; on ultracentrifugation, a faster-sedimenting fraction, to an extent of 5–8% only, was observed in each case. 2. Similar physical properties were exhibited by these glycoproteins and they each have a molecular weight of about 105000. 3. In chemical composition, differences have been observed and the glycoproteins can be classified into three groups: (a) sheep and goat glycoproteins; (b) cow and buffalo glycoproteins; (c) monkey glycoprotein. Glucose, galactosamine and N-terminal amino acid were absent from these proteins. 4. These glycoproteins were trypsin inhibitors and prolonged the clotting time of plasma.     

Neocarzinostatin: an antitumor protein a preliminary x-ray diffraction study.

The antitumor protein, neocarzinostatin, has been crystallized and examined by X-ray diffraction. Crystals of this globular protein are of space group P2₁2₁2₁ with cell parameters a = 27.4Å, b = 33.9Åand c = 102.0Å. There is one molecule of approximately 27Ådiameter per asymmetric unit. Crystals soaked in a K₂HgI₄ solution give diffraction patterns significantly different from native crystal diffraction patterns.