Equivalence-point electromigration acid-base titration via moving neutralization boundary electrophoresis.

In this paper, we developed a novel method of acid-base titration, viz. the electromigration acid-base titration (EABT), via a moving neutralization boundary (MNR). With HCl and NaOH as the model strong acid and base, respectively, we conducted the experiments on the EABT via the method of moving neutralization boundary for the first time. The experiments revealed that (i) the concentration of agarose gel, the voltage used and the content of background electrolyte (KCl) had evident influence on the boundary movement; (ii) the movement length was a function of the running time under the constant acid and base concentrations; and (iii) there was a good linearity between the length and natural logarithmic concentration of HCl under the optimized conditions, and the linearity could be used to detect the concentration of acid. The experiments further manifested that (i) the RSD values of intra-day and inter-day runs were less than 1.59 and 3.76%, respectively, indicating similar precision and stability in capillary electrophoresis or HPLC; (ii) the indicators with different pK(a) values had no obvious effect on EABT, distinguishing strong influence on the judgment of equivalence-point titration in the classic one; and (iii) the constant equivalence-point titration always existed in the EABT, rather than the classic volumetric analysis. Additionally, the EABT could be put to good use for the determination of actual acid concentrations. The experimental results achieved herein showed a new general guidance for the development of classic volumetric analysis and element (e.g. nitrogen) content analysis in protein chemistry.

Assessing computational amino acid beta-turn propensities with a phage-displayed combinatorial library and directed evolution.

Structure propensities of amino acids are important determinants in guiding proteins' local and global structure formation. We constructed a phage display library--a hexa-HIS tag upstream of a CXXC (X stands for any of the 20 natural amino acids) motif appending N-terminal to the minor capsid protein pIII of M13KE filamentous phage--and developed a novel directed-evolution procedure to select for amino acid sequences forming increasingly stable beta-turns in the disulfide-bridged CXXC motif. The sequences that emerged from the directed-evolution cycles were in good agreement with type II beta-turn propensities derived from surveys of known protein structures, in particular, Pro-Gly forming a type II beta-turn. The agreement strongly supported the notion that beta-turn formation plays an active role in initiating local structure folding in proteins.

Modulatory action of endogenous and exogenous nitric oxide on survival of alveolar macrophages from normal and bleomycin-treated rats.

To investigate the modulatory action of endogenous and exogenous nitric oxide (NO) on survival of alveolar macrophages (AMs) in different cellular states, AMs from normal rats (normal AMs) and from bleomycin (BLM)-treated rats (BLM AMs) were incubated by sodium nitroprusside (SNP, NO donor) and L-arginin (L-Arg, NO precursor), respectively. The survival of AMs was evaluated by apoptosis and cell cycles. The molecular mechanisms were investigated by the contents of Bcl-2, Bax proteins in AMs. The results are as follows: (1) The degree of BLM AMs apoptosis was higher than that of normal AMs; the number of BLM AMs in G(0)/G(1) phases was less than that of normal AMs; there was no significant difference in S+G(2)M phases between the number of BLM AMs and that of normal AMs. (2) Down-regulation of Bcl-2 and up-regulation of Bax occurred in BLM AMs, compared to those in normal AMs. (3) Apoptosis of AMs, either normal AMs or BLM AMs, was induced by both SNP and L-Arg, when compared to their respective control; only the number of BLM AMs in S+G(2)M phases was increased by L-Arg. (4) SNP and L-Arg induced a down-regulation of Bcl-2 and an up-regulation of Bax proteins in normal AMs, but did not induce the same change pattern in BLM AMs. (5) The Bax in BLM AMs was down-regulated by L-Arg. It is concluded that NO can induce the apoptosis of BLM AMs and normal AMs; that Bcl-2 and Bax are implicated in NO-induced apoptosis of normal AMs, whereas they are not involved in that of BLM AMs, suggesting the differential molecular mechanisms underlying the NO-induced apoptosis of normal AMs and BLM AMs; and that endogenous NO promotes proliferation of BLM AMs, which might be associated with down-regulation of Bax.

Role of endogenous peroxynitrite in pulmonary injury and fibrosis induced by bleomycin A5 in rats.

AIM: To observe the role of endogenous peroxynitrite (ONOO-) in pulmonary injury and fibrosis induced by bleomycin A5 (BLM-A5) in rats. METHODS: Pulmonary injury and fibrosis of rats were evaluated by testing the level of lipid peroxides (LPO) in out-going pulmonary blood (OPB), and by observing histological changes, including type III and type I collagen changes in lung which were examined with Sirius red staining under polarized light. The peroxynitrite expression was detected by immunohistochemistry for nitrotyrosine (NT), a marker of the peroxynitrite production. RESULTS: (1) The level of LPO was elevated in OPB of rats on d 14 after intratracheal administration of BLM-A5. Thickened alveolar wall and macrophage infiltration were seen, and fibroblasts were near by the interstitial macrophages. Increased amounts of type III collagen and type I collagen were deposited in disoriented fashion. (2) High expression of ONOO- was detected in alveolar epithelial cells and pulmonary interstitial macrophages. (3) The above changes were reduced by aminoguanidine (AG), an inhibitor of nitric oxide synthase (iNOS). CONCLUSION: Endogenous ONOO- mediated BLM-A5-induced pulmonary toxicity. The therapeutic potential of AG for pulmonary injury and fibrosis was realized partly by reducing ONOO- formation.