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Peptide permeability

The lungs large, permeable surface makes systemic deUvery possible. For example, an inhaler deUvers 360 )Tg per dose of aerosolized ergotamine tartrate [379-79-3] for migraine (54), and inhalant systems deUver anesthetic gases. Research is under way on the systemic deUvery of proteins and peptides through the lungs (57,58). [Pg.142]

Sephadex type Grade Dry bead diameter (/urn) Fractionation range peptides and proteins (g/mol) Fractionation range dextrans (g/mol) Swelling factor (ml/g dry Sephadex) Maximum operating pressure" (cm H,0) Permeability Ko Maximum linear velocity" (cm/hr) Swelling time (h) ... [Pg.40]

The transmembrane potential derived from a concentration gradient is calculable by means of the Nemst equation. If K+ were the only permeable ion then the membrane potential would be given by Eq. 1. With an ion activity (concentration) gradient for K+ of 10 1 from one side to the other of the membrane at 20 °C, the membrane potential that develops on addition of Valinomycin approaches a limiting value of 58 mV87). This is what is calculated from Eq. 1 and indicates that cation over anion selectivity is essentially total. As the conformation of Valinomycin in nonpolar solvents in the absence of cation is similar to that of the cation complex 105), it is quite understandable that anions have no location for interaction. One could with the Valinomycin structure construct a conformation in which a polar core were formed with six peptide N—H moieties directed inward in place of the C—O moieties but... [Pg.211]

The blood-brain barrier (BBB) forms a physiological barrier between the central nervous system and the blood circulation. It consists of glial cells and a special species of endothelial cells, which form tight junctions between each other thereby inhibiting paracellular transport. In addition, the endothelial cells of the BBB express a variety of ABC-transporters to protect the brain tissue against toxic metabolites and xenobiotics. The BBB is permeable to water, glucose, sodium chloride and non-ionised lipid-soluble molecules but large molecules such as peptides as well as many polar substances do not readily permeate the battier. [Pg.272]

More than 50 endogenous and exogenous inhibitors of the calpains have been described as either transition-state reversible or irreversible inhibitors. The first transition-state inhibitors were the peptide aldehydes (e.g., leupeptin). Using this compound, new ones were synthesized that exhibited improved membrane permeability and calpain specificity (e.g., calpeptin). Other groups of inhibitors have since been discovered a-dicarbonyls (originally developed as serine protease inhibitors), nonpeptide quinolinecarboxamides,... [Pg.313]

B. G. Phospholipid membrane permeability of peptide nucleic acid. FEB. S. Lett. [Pg.175]

Nasal Administration. The nasal mucosa is relative permeable to small molecular weight compounds. The most notorious example is cocaine. Cocaine that is snorted is both rapidly and extensively absorbed. Small peptides have also been successfully administered nasally, although the bioavailability is low. However, where the availability is not critical, nasal administration of peptides has been successful. The best example is... [Pg.136]

Vasopressin is a peptide hormone produced by the hypothalamus and secreted by the posterior pituitary in response to stimulation. Normal stimuli for vasopressin release are hyperosmolarity and hypovolemia, with thresholds for secretion of greater than 280 mOsm/kg and greater than 20% plasma volume depletion. A number of other stimuli, such as pain, nausea, epinephrine, and numerous drugs, induce release of vasopressin. Vasopressin release is inhibited by volume expansion, ethanol, and norepinephrine. The physiological effect of vasopressin is to promote free water clearence by altering the permeability of the renal collecting duct to water. In addition, it has a direct vasoconstrictor effect. Consequently, vasopressin results in water retention and volume restoration. In patients with septic shock, vasopressin is appropriately secreted in response to hypovolemia and to elevated serum osmolarity (R14). [Pg.97]

Poduslo JF, Curran GL, Kumar A, Frangione B, Soto C. Beta-sheet breaker peptide inhibitor of Alzheimer s amyloidogenesis with increased blood-brain barrier permeability and resistance to proteolytic degradation in plasma. J Neurobiol 1999 39 371-382. [Pg.279]

WATER WIRES, H+/OH CURRENTS, AND THE PERMEABILITY OF AMINO ACIDS AND PEPTIDES... [Pg.73]

Using liposomes made from phospholipids as models of membrane barriers, Chakrabarti and Deamer [417] characterized the permeabilities of several amino acids and simple ions. Phosphate, sodium and potassium ions displayed effective permeabilities 0.1-1.0 x 10 12 cm/s. Hydrophilic amino acids permeated membranes with coefficients 5.1-5.7 x 10 12 cm/s. More lipophilic amino acids indicated values of 250 -10 x 10-12 cm/s. The investigators proposed that the extremely low permeability rates observed for the polar molecules must be controlled by bilayer fluctuations and transient defects, rather than normal partitioning behavior and Born energy barriers. More recently, similar magnitude values of permeabilities were measured for a series of enkephalin peptides [418]. [Pg.74]

Hu Ming, HI Mosberg, GL Amidon. Use of the peptide carrier system to improve the intestinal absorption of L-alpha-methyldopa Carrier kinetics, intestinal permeabilities, and in vitro hydrolysis of dipeptidyl derivatives of L-alpha-methyldopa. Pharm Res 6(1) 66—69, 1989. [Pg.232]


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See also in sourсe #XX -- [ Pg.2752 ]




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