Study of furanose ring flexibility in polynucleotide chains using Raman spectra analysis

The bands within the range of 800–850 cm^?1 of Raman spectra of polynucleotides sensitive to the change in conformation of sugar–phosphate backbone are analyzed theoretically. The bands are interpreted as the appearance of a quasi-local deoxyribose vibrational mode whose frequency is dependent on the ring puckering. The localization region of the vibrational mode is pointed out. The theory establishes a relationship between the observed spectral intensity and the population of deoxyribose conformational states described in the framework of the pseudorotation concept. The approach developed allowed one to describe the band shapes and their temperature behavior, and to determine the pseudorotation potential of deoxyribose in the helix B -form of A · T containing polynucleotides. Using the analysis of Raman spectra of DNA fibers in water–ethanol mixture the deoxyribose flexibility during the B -A transition is investigated in terms of the population of conformers and effective potential. It is shown that N- and S-type deoxyribose conformers are populated in the DNA B -form (those of the S-type are preferable), whereas N-type conformers are primarily populated in the DNA A -form.     

Effect of interstitial edema on lung lymph flow in goats in the absence of filtration.

We tested the effect of interstitial edema on lung lymph flow when no filtration occurred. In 16 anesthetized open-thorax ventilated supine goats, we set pulmonary arterial and left atrial pressures to nearly zero and measured lymph flow for 3 h from six lungs without edema and ten with edema. Lymph flow decreased exponentially in all experiments as soon as filtration ceased. In the normal lungs the mean half time of the lymph flow decrease was 12.7 +/- 4.8 (SD) min, which was significantly shorter (P less than 0.05) than the 29.1 +/- 14.8 min half time in the edematous lungs. When ventilation was stopped, lymph flow in the edematous lungs decreased as rapidly as in the normal lungs. The total quantity of lymph after filtration ceased was 2.7 +/- 0.8 ml in normal lungs and 9.5 +/- 6.3 ml in edematous lungs, even though extravascular lung water was doubled in the latter (8.4 +/- 2.4 vs. 3.3 +/- 0.4 g/g dry lung, P less than 0.01). Thus the maximum possible clearance of the interstitial edema liquid by the lymphatics was 6.3 +/- 4.8%. When we restarted pulmonary blood flow after 1-2 h in four additional goats, lymph flow recovered within 30 min to the baseline level. These findings support the hypothesis that lung lymph flow originates mainly from alveolar wall perimicrovascular interstitial liquid and that the contribution of the lung lymphatic system to the clearance of interstitial edema (bronchovascular cuffs, interlobular septa) is small.     

Status of the capillary endothelium of the lung in normovolemic perfusion of the organ through the system of the pulmonary artery

Pulmonary perfusion for 30 min to the dog under conditions of normovolemia is not accompanied with any essential changes in parameters of alveolar capillaries endothelium. Just the opposite, transformation of endothelial lining of the peribronchial capillaries demonstrates possible disturbances of the liquor transport across the walls of these vessels. The volumetric part of the interstitial space near these capillaries increases, while in the alveolar septa it does not change. In lymph formation, flowing out of the lung, together with bronchial capillaries, blood capillaries of the alveoli must take part.     

Transport of a fluid in the lung interstitial space. A model of porous medium with distributed parameters

Velocity and behaviour of the fluid stream into lung interstitium was experimentally evaluated during and after hydrodynamic loading. A mathematical model of unsteady fluid movement in interstitium able to relaxation was proposed.