Proteins absorption

D. gigas AOR was the first Mo-pterin-containing protein whose 3D structure was solved. From D. desulfuricans, a homologous AOR (MOD) was purified, characterized, and crystallized. Both proteins are homodimers with-100 kDa subunits and contain one Mo-pterin site (MCD-cofactor) and two [2Fe-2S] clusters. Flavin moieties are not found. The visible absorption spectrum of the proteins (absorption wavelengths, extinction coefficients, and optical ratios at characteristic wavelengths) are similar to those observed for the deflavo-forms of... 

CARVALHO M R, SGARBiERi V 0 (1998) Relative importance of phytohemagglutinin (lectin) and trypsin-chymotrypsin inhibitor on bean (Phaseolus vulgaris L) protein absorption and utilization by the rat. JNutr Sci Vitaminol (Tokyo). 44 685-96. 

Protein Absorption Maximum (nm) Rotation Amplitude per mole... 

Although the detailed mechanism of the longer circulation time of branched PEGylated protein is unclear, the architecture of PEG affects the release profile, the pharmacokinetics of the chug [29], and the behavior of the protein at the interface (e.g., protein absorption on hydrophobic surfaces [30]). 

Antibodies produced by this procedure were screened for their ability to react with the hapten to form the vinylogous amide 6, which has a convenient UV chromophore near 318nm, clear of the main protein absorption. Two antibodies selected in this way catalysed the expected aldol reaction of acetone with aldehyde 7 by way of the enamine 8 (Scheme 3) the remainder did not. These two effective aldolase mimics have been studied in some detail, and a crystal structure is available for (a Fab fragment of) one of them.126,281... 

Muller et al.understand better the role of tyrosine in the structure and biological function of MDH. Resolution of the protein absorption spectrum, using iV-acetylphenylalanine ethyl ester in dioxane and A-acetyltyrosine ethyl ester in dioxane or 0.1 M phosphate buffer to model the effect of the local environments of the chromophoric groups, indicated that both the pig and the... 

Portero A, Remunan-Lopez C, and Nielsen HM (2002) The potential of chitosan in enhancing peptide and protein absorption across the TR146 cell culture model—An in vitro model of the buccal mucosa. Pharm. Res. 19 169-174. 

Although there appears to be no significant species differences in absorption rates for small lipophilic drugs, some interspecies differences are noted with water-soluble drugs absorbed from distal airspaces of in vivo mammalian lungs [112], These species differences have not been systematically studied yet. However, some marked differences were reported for protein absorption rates... 

Proteases occurring in the epithelial lining fluids are another source of variability in protein absorption from the lung. In the epithelial lining fluids proteases and peptidases do occur. Inhibition of proteases and peptidases with substances such as bacitracin or aprotinin might improve the bioavailability of proteins. For example bacitracin was shown to increase insulin bioavailability by a factor of 6.8 [3]. 

Burton, P.S., Conradi, R.A. and Hilgers, A.R. (1991) Mechanisms of peptide and protein absorption. (2). Transcellular mechanism of peptide and protein, absorption passive aspects. Advanced Drug Delivery Reviews, 7, 365-386. 

Raloxifene (Evista) is a new SERM approved for use in the treatment and prevention of osteoporosis because it has estrogenic activity in bone. Raloxifene is an estrogen antagonist in both breast and endometrial tissues. The estrogenhke properties of raloxifene result in the maintenance of a favorable serum Upid profile (decreased low-density lipoprotein levels with no change in either high-density lipoproteins or triglycerides). Raloxifene is 95% bound to plasma proteins. Absorption of raloxifene is impaired by cholestyramine. 

The impact of formulation on protein absorption and disposition is also an important factor in the development and use of biologic molecules. Stability of the protein drug in subcutaneous or muscle tissues and absorption rates directly influence the overall response. Various physical and chemical approaches are used to stabilize proteins and other macromolecules as a part of optimizing dosage formulations. 

Since aromatic amino acids and cysteine are absent, there is no protein absorption above 270 nm. Metallothioneins exhibit a broad absorption peak, with the maximum at 190 mn. Absorptions due to the metal-thiolate complexes show as shoulders at 250 nm (Cd), 220 nm (Zn) and 270 nm (Cu).1458,1459 Theoretical predictions based on the amino acid sequence of the peptide chain indicate that the or-helical conformation is forbidden, and /3-structure is almost impossible to attain. CD and NMR studies on both the metal-containing and metal-free protein confirmed the predictions.1459 1460 However, metallothioneins are stable to tryptic digestion and the slow exchange of many peptide hydrogens of metallothionein with those of the solvent suggest that the protein has a compact and well-defined tertiary structure. 

The effect is much more marked if a third component that absorbs in the wavelength range of the protein absorption or fluorescence is added to the solution (see Basic Protocol 2). 

The molecular weight of 320,000 obtained for the muscle enzyme from sedimentation-diffusion data at 2-6 mg/ml and v = 0.75 (132) is to be compared with 270,000 obtained by Wolfenden et al. from s20,w = 11.1 S and D2 ,w = 3.75 X 10 7 cm2 sec1, and v = 0.731 calculated from the amino acid content (92). The rabbit muscle enzyme has a normal amino acid content, that is, no unusually low or large amount of a particular amino acid was found. Of the 32 cysteine/half-cystine residues per mole based on a molecular weight of 270,000, 6.2 were rapidly titrated with p-mercuribenzoate (92). Typical protein absorption spectra were reported for elasmobranch fish (126), carp (125), rat (127), and rabbit muscle enzyme (68). An E m at 280 nm = 9.13 has been reported for the rabbit muscle enzyme (133). The atypical absorption spectrum with a maximum at 275-276 nm observed by Lee (132) is indicative of contaminating bound nucleotides. 

Because protein absorption maxima in the near-ultraviolet (240-300 nm) are determined by the content of the... 

Nellans, H.N. 1991. Mechanism of peptide and protein absorption, paracellular intestinal transport Modification of absorption. Adv Drug Deliv Rev 7 339. 

Lee, V.H. 1988. Enzymatic barriers to peptide and protein absorption. Crit Rev Ther Drug Carrier Syst 5 69. 

In recent years, efforts have been made to find methods to increase peptide and protein absorption via the vaginal mucosa by the use of penetration enhancers, enzyme inhibitors, and bioadhesive drug delivery systems. 

Fig. 4. Schematic of a single-step array fabrication process for in vivo biotinylated proteins. Step a A cmde lysate containing the desired biotinylated recombinant protein is printed onto a streptavidin-coated surface coderivatized with a polymer that resists nonspecific protein absorption. Step b Unbound proteins are washed away to leave the purified recombinant protein, specifically immobilized and oriented on the array surface via the biotin moiety on the BCCP tag.

Alveolar epithelium and local proteases are believed to be the major barriers for the efficient absorption of inhaled proteins and peptides. Many novel and potent absorption enhancers have been investigated for the peptide/protein absorption... 

Mechanisms of Protein Absorption after Pulmonary Delivery... 

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