potassium-thiocyanate and potassium-nitrate

Collagen can be modified by addition of chaotropic or kosmotropic salts of the reversed Hofmeister series. Hence, telopeptide-poor collagen type I was suspended in H2SO4 (pH 2) and 0.05-0.5 M KCl and KNO3 (chaotropes), as well as KI and KSCN (kosmotropes). Rheological parameters, including storage and loss modulus, intrinsic viscosity, and critical overlap concentration, were assessed and the microstructure was characterized by applying confocal laser scanning microscopy and scanning electron microscopy. The addition of up to 0.1 M KCl and 0.05 M KNO3 increased the intrinsic viscosity from 1.22 to 1.51 L/g without salt to a maximal value of 1.74 L/g and decreased the critical overlap concentration from 0.66 to 0.82 g/L to a minimal value of 0.57 g/L. Higher salt concentrations increased the collagen-collagen interactions due to ions withdrawing the water from the collagen molecules. Hence, 0.1 M KSCN delivered the largest structures with the highest structure factor, area value and the highest critical overlap concentration with 17.6 L/g. Overall, 0.5 M salt led to salting out, with chaotropes forming fine precipitates and kosmotropes leading to elastic three-dimensional networks. The study demonstrated that collagen entanglement and microstructure depend strongly on the ionic strength and type of salt.

Topics: Collagen Type I; Hydrogen-Ion Concentration; Nitrates; Potassium Chloride; Potassium Compounds; Potassium Iodide; Protein Aggregates; Salts; Sulfuric Acids; Thiocyanates; Viscosity

We have explored the structure and subunit composition of the vacuolar ATPase of Neurospora crassa by investigating the effects of nitrate. Inhibition of enzyme activity by nitrate was correlated with dissociation of a complex of peripheral polypeptides from the integral membrane part of the enzyme. Surprisingly, this nitrate-induced release of subunits occurred only when nucleotides such as ADP, ATP, or ITP were present. ATPase inhibitors that have been proposed to act at the active site prevented release of subunits. Six polypeptides, 67, 57, 51, 48, 30, and 16 kDa, were coordinately released from the vacuolar membrane. When analyzed by size exclusion chromatography or by centrifugation through glycerol gradients, the six polypeptides behaved as an aggregate of about 440,000 kDa. We also examined vacuolar membranes by electron microscopy, using negative staining. We observed a high density of "ball and stalk" structures on the membranes, similar in size but different in shape from the F0F1-ATPase of mitochondrial membranes. Treatment with nitrate removed the ball and stalk structures from vacuolar membranes but had no visible effect on mitochondrial membranes. We concluded that the overall structure of the vacuolar ATPase is similar to that of F0F1-ATPases; however, the sizes of the component polypeptides and the factors that can cause dissociation are different.

Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Intracellular Membranes; Kinetics; Macromolecular Substances; Microscopy, Electron; Mitochondria; Neurospora; Neurospora crassa; Nitrates; Potassium Compounds; Proton-Translocating ATPases; Thiocyanates; Vacuoles

In vivo delta-9-tetrahydrocannabinol (delta-9-THC) under short (10 and 50 mg/kg) and long term (10 mg/kg/day for 15 consecutive days) administration (i.p.) to adult male albino rats increased the mitochondrial swelling of hypothalamus, heart and liver. Similarly, in vitro treatment with delta-9-THC (2-8 micrograms/mg protein) produced a dose-dependent stimulation in the mitochondrial swelling of different tissues. Ca2+ ions (0.15 mM - 0.3 mM) increased the mitochondrial swelling. Calcium (0.3 mM)-induced stimulation of mitochondrial swelling was enhanced with delta-9-THC under both in vivo and in vitro conditions. Chaotropic agents e.g. KNO3 (100-200 mM) and KSCN (200-400 mM), decreased the mitochondrial swelling. Chaotropic (200 mM)-induced inhibitory effect in different tissues was reduced with delta-9-THC under in vivo and in vitro treatments. These results suggest that delta-9-THC, like calcium, stimulated the mitochondrial swelling, and that the action of delta-9-THC may be localized on the specific structures of the membrane which are sensitive to chaotropic agents.

Topics: Animals; Calcium; Dronabinol; In Vitro Techniques; Male; Mitochondrial Swelling; Nitrates; Potassium Compounds; Rats; Thiocyanates