Increasing the in vitro bile acid binding capacity of diethylaminoethylcellulose by quaternization.

Diethylaminoethylcellulose (DEAE-cellulose) was quaternized with methyl iodide (DEAE-cellulose-CH3I), and its in vitro binding capacity for sodium glycocholate, at room temperature, in water, Tris-HCl buffer (0.0015-0.0050 M, pH 7.0), and aqueous NaCl (0.0025 M) was determined by reversed-phase HPLC. Quaternization increased the in vitro bile salt binding capacity of DEAE-cellulose. On a molar basis, the binding capacity was greater than that of cholestyramine, a cholesterol-lowering agent. Increasing the ionic strength of the medium decreased the binding capacities, as expected if ionic interactions are important. However, conversion of DEAE-cellulose-CH3I to its chloride form did not change the binding capacity. The bile salt binding capacity of DEAE-cellulose-CH3I was similar for both sodium cholate and sodium glycocholate.

Interaction of cellulose-based cationic polyelectrolytes with mucin.

Mucoadhesivity of water-soluble polymers is an important factor, when testing their suitability for controlled drug delivery systems. For this purpose, the interaction of new cationic cellulose polyelectrolytes with lyophilized mucin was investigated by means of turbidimetric titration, microscopy and measurement of zeta potential and particle size changes in the system. Results show that the cellulose derivatives interact with mucin. This interaction became stronger if cellulose macromolecules contained positively charged groups and an electrostatic interaction with the negatively charged mucin particles occurred. Under certain conditions flocculation of mucin particles by the cellulose polyelectrolyte was observed.

Differential effect toward inhibition of papain and cathepsin C by recombinant human salivary cystatin SN and its variants produced by a baculovirus system.

Human salivary cystatin SN (CsnSN) is a member of the cystatin superfamily of cysteine proteinase inhibitors. In this study we used a baculovirus expression system to produce a full-length unaltered CsnSN and its variants. The variants were constructed with the changes in the three predicted proteinase-binding regions: the N-terminus (variant N(12-13), G12A-G13A), beta-hairpin loop I (variant L(56-58), Q56G-T57G-V58G) and beta-hairpin loop II (variant L(106-107), P106G-W107G). The secreted CsnSNs were purified using sequential spiral cartridge ultrafiltration and DE-52 radial flow chromatography. The purified proteins were examined for papain- and cathepsin C-inhibition. The wild-type CsnSN, and variants N(12-13) and L(106-107) bound tightly to papain (K(i) < 10 pM), whereas mutation in the loop I reduced binding affinity 5700-fold (K(i) = 57 nM). On the other hand, the wild-type CsnSN bound to cathepsin C less tightly (K(i) = 100 nM). The mutation in the N-terminus or loop I reduced binding affinity by 16 (K(i) = 1.6 microM)- and 19-fold (K(i) = 1.9 microM), respectively, while mutation in loop II resulted in an ineffective cathepsin C inhibitor (K(i) = 14 microM). Collectively, these results suggest that the N-terminal G12-G13 residues of CsnSN are not essential for papain inhibition but play a role in cathepsin C inhibition; residues Q56-T57-V58 in the loop I are essential for both papain and cathepsin C inhibitions, and residues P106-W107 in the loop II are not important for papain inhibition but essential for cathepsin C inhibition. These results demonstrated that CsnSN variants have different effects toward different cysteine proteinases.

The use of diethylaminoethyl-cellulose-membrane filters in a bioassay to quantify melanin synthesis.

Melanins are a class of extremely insoluble granular biopolymers with a yet ill-defined chemical structure, properties which render the isolation and quantification of these molecules very difficult. Based on their strong anionic character, however, a biophysical property shared by all melanins, we have developed a method allowing total recovery of the pigment. Soluble melanin is bound and granular melanin retained by DEAE-cellulose membrane filters. This approach provides an excellent means to quantify melanin synthesis in normal human melanocytes alone and in coculture with normal human keratinocytes.