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Ferroelectric surfaces can have very high surface charge densities that can be harnessed for manipulation of charged colloidal particles and soft matter in aqueous environments. Here, we report on the electrical double layer (EDL) formed by polarized ultrasmooth lead zirconium titanate (US-PZT) thin films in dilute electrolyte solutions. Using colloidal probe force microscopy (CPFM) measurements, we show that the ion distribution within the double layer can be changed by reversing the ferroelectric polarization state of US-PZT. The interaction force in dilute 1:1 electrolyte solution between the negatively charged probe and a positive surface charge (upward polarized) US-PZT thin film is attractive, while the interaction force is repulsive for a negative surface charge (downward polarized) film. We modeled these interactions with a constant-potential EDL model between dissimilar surfaces with the inclusion of a Stern layer. We report the surface potentials at the inner and outer-Helmholtz planes both for polarization states and for a range of ionic strength solutions. Effects of free-charge carriers, limitations of the analytical model, and effects of surface roughness are discussed.

1. There is good evidence that acid is a prerequisite for aspirin induced gastric mucosal damage; however, there is inconsistent information available for non-salicylate NSAID. The present study examines the effect of gastric luminal pH on indomethacin-induced gastric mucosal damage. 2. Macroscopic gastric mucosal damage induced by indomethacin (40 mg/kg) or vehicle, administered intraduodenally to male pylorus-ligated rats (n = 5-10/group), was assessed at four different levels of luminal pH (2,4,5.5 and 7) by means of digital planimetry. 3. There was a marked difference in the extent of damage induced by indomethacin at the different luminal pH levels (P = 0.001). There was no difference between the percentage of haemorrhagic lesions at pH 2 and 4 (P > 0.05), nor between pH 5.5 and 7 (P > 0.05). However, the damage at the high levels of luminal acidity (pH 2 and 4) was strikingly different from that at pH 5.5 and 7 (P < 0.05). 4. Gastric mucosal damage induced by indomethacin, a non-salicylate NSAID, is augmented by the presence of high concentration of acid in the gastric lumen. The main finding, that indomethacin injury is markedly less above pH 4, may have clinical implications in the prevention of NSAID-induced mucosal injury.

Reverse-phase high-performance liquid chromatography has been used to fractionate ribosomal proteins from Escherichia coli and rabbit reticulocytes. Different column packing materials and solvent systems were compared for their effectiveness with bacterial proteins. A large-pore (300 A) short alkyl chain support (Altex RPSC) in conjunction with a triethylamine phosphate (pH 2.2)/acetonitrile solvent system was particularly effective and separated mixtures of total protein from each ribosomal subunit into a number of peaks approaching the actual number of proteins present. For example, with the use of the Altex RPSC column, the 21 proteins of 30S subunits were resolved into 18 distinct peaks, and the 33 proteins of the 50S subunits were resolved into 28 peaks. Overall recovery varied from 75% to 90% in different experiments. The composition of each peak was established by two-dimensional gel electrophoresis. Relatively acidic proteins, for example, S1 and L7/L12 of Escherichia coli, were bound more tightly to the column and recovered in lower yields than the other more basic proteins. Proteins that were incompletely resolved in a single step could be obtained in pure form by rechromatography on the same column with an altered gradient or with a different type of reverse-phase packing material. Ribosomal proteins from rabbit reticulocytes were also separated with good resolution and yield by using the RPSC column.

Met-hemoglobin, cross-linked with [14C]dimethyladipimidate (cross-linking span 9 A; 1 A = 0.1 nm), yields four distinct molecular weight products (monomer, dimer, trimer, and tetramer) as observed on sodium dodecyl sulfate - polyacrylamide gels. The dimer species was purified to homogeneity by gel filtration. It was proteolytically degraded using a combination of Staphylococcus aureus V8 protease, pepsin, trypsin, and chymotrypsin. The resultant peptides were fractionated using gel filtration and ion-exchange chromatography methods. Two cross-links were unambiguously identified: (i) alpha 1Lys7-alpha 1Lys11 and (ii) beta 1Lys82-beta 2Lys82. The identified cross-links correlated well with the known structure of hemoglobin. However, attempts to isolate and identify a greater number of cross-linked peptides were unsuccessful owing to the complexity of the peptide mixtures. The complexity was a direct result of the chemical modification of the hemoglobin molecule. Therefore, attempts to employ chemical cross-linking as a means of examining sites of protomer contact within large oligomeric proteins should be approached with caution.

An immunotoxin composed of an antibody to the human transferrin receptor (454A12) and ricin A chain (RTA) was shown to inhibit the growth of NIH:OVCAR-3 tumors in a nude mouse model of human ovarian cancer. Inhibition of tumor growth by 454A12-RTA was related to the dose administered. The antitumor activity of the immunotoxin was blocked by coinjection of excess antibody with immunotoxin. An immunotoxin made using 454A12 and recombinant ricin A chain (rRTA) had an activity similar to that made with native RTA. The administration of 10 micrograms or greater of the immunotoxin 454A12-RTA/rRTA had significant antitumor activity. The injection of 30 micrograms of an irrelevant immunotoxin, MOPC21-RTA, or 30 to 500 micrograms of the 454A12 antibody had no antitumor activity.