Antimicrobial Activity and Protease Stability of Peptides Containing Fluorinated Amino Acids

Selective fluorination of peptides results in increased chemical and thermal stability with simultaneously enhanced hydrophobicity. We demonstrate here that fluorinated derivatives of two host defense antimicrobial peptides, buforin and magainin, display moderately better protease stability while retaining, or exhibiting significantly increased bacteriostatic activity. Four fluorinated analogues in the buforin and two in the magainin series were prepared and analyzed for (1) their ability to resist hydrolytic cleavage by trypsin; (2) their antimicrobial activity against both Gram-positive and Gram-negative bacterial strains; and (3) their hemolytic activity. All but one fluorinated peptide (M2F5) showed retention, or significant enhancement, of antimicrobial activity. The peptides also showed modest increases in protease resistance, relative to the parent peptides. Only one of the six fluorinated peptides (BII1F2) was degraded by trypsin at a slightly faster rate than the parent peptide. Hemolytic activity of peptides in the buforin series was essentially null, while fluorinated magainin analogues displayed an increase in hemolysis compared to the parent peptides. These results suggest that fluorination may be an effective strategy to increase the stability of biologically active peptides where proteolytic degradation limits therapeutic value

Correlations of R₁₀ with the variations of SOC, soil TN, and soil P in broadleaved and mixed forests.

<p>Correlations of R₁₀ with the variations of SOC, soil TN, and soil P in broadleaved and mixed forests.</p

Relationships of Q₁₀ with variation of herbaceous carbon stock in both forest types.

<p>Relationships of Q₁₀ with variation of herbaceous carbon stock in both forest types.</p

Relationships between soil chemical properties and Q₁₀ respectively in broadleaved and mixed forest types.

<p>Relationships between soil chemical properties and Q₁₀ respectively in broadleaved and mixed forest types.</p

Variation in basal parameters of soil respiration within or between forest types.

<p>The significance of differences of basal parameters between forest types were separately tested by independent t - test (two - tailed) at α = 0.05 (n = 9 in the broadleaved forest, and 11 in the mixed forest). Same lowercase letter means no significant difference is detected at α = 0.05 within 95% confidence interval between the two forest types.</p

The effects of biophysical variables on R₁₀ and Q₁₀ analyzed by the method of Redundancy Analysis (RDA).

<p>SBD: soil bulk density; DBH: diameter at breast height.</p>a<p>Describe marginal effects, which shows the variance when the variable is used as the only factor.</p>b<p>Describe conditional effects, which shows the additional variance each variable explains when it is included in the model.</p>c<p>The level of significance corresponding to Lambda-A when performing Monte Carlo test (with 499 random permutations) at the 0.05 significance level.</p>d<p>The Monte Carlo test statistics corresponding to Lambda-A at the 0.05 significance level.</p

Correlations of R₁₀ with basal area and CV of shrub carbon stock separately for both forest types.

<p>Correlations of R₁₀ with basal area and CV of shrub carbon stock separately for both forest types.</p

Chemical Denaturation and Protein Precipitation Approach for Discovery and Quantitation of Protein–Drug Interactions

Described here is a mass spectrometry-based proteomics approach for the large-scale analysis of protein–drug interactions. The approach involves the evaluation of ligand-induced protein folding free energy changes (ΔΔGf) using chemical denaturation and protein precipitation (CPP) to identify the protein targets of drugs and to quantify protein–drug binding affinities. This is accomplished in a chemical denaturant-induced unfolding experiment where the folded and unfolded protein fractions in each denaturant containing buffer are quantified by the amount of soluble or precipitated protein (respectively) that forms upon abrupt dilution of the chemical denaturant and subsequent centrifugation of the sample. In the proof-of-principle studies performed here, the CPP technique was able to identify the well-known protein targets of cyclosporin A and geldanamycin in a yeast. The technique was also used to identify protein targets of sinefungin, a broad-based methyltransferase inhibitor, in a human MCF-7 cell lysate. The CPP technique also yielded dissociation constant (Kd) measurements for these well-studied drugs that were in general agreement with previously reported Kd or IC50 values. In comparison to a similar energetics-based technique, termed stability of proteins from rates of oxidation (SPROX), the CPP technique yielded significantly better (∼50% higher) proteomic coverage and a largely reduced false discovery rate

Relationships of Q₁₀ with soil physical factors separately in broadleaved and mixed forest types.

<p>Relationships of Q₁₀ with soil physical factors separately in broadleaved and mixed forest types.</p