Unlocking the Latent Antimicrobial Potential of Biomimetically Synthesized Inorganic Materials

Inspired by biomineralization, biomimetic approaches utilize biomolecules and synthetic analogs to produce materials of controlled chemistry, morphology, and function under relatively benign conditions. A common characteristic of biological and biomimetic mineral‐forming processes is the generation of mineral/biomolecule nanocomposites. In this work, it is demonstrated that a facile chemical reaction may be utilized to halogenate the nitrogen‐containing moieties of the organics entrapped within bio‐inorganic composites to yield halamine compounds. This process provides rapid and potent bactericidal activity to biomimetically and biologically produced materials that otherwise lack such functionality. Additionally, bio‐inorganic composites containing the chlorinated peptide protamine are effective in rapidly neutralizing Bacillus spores (≥99.97% reduction in colony forming units within 10 min). The straightforward nature of the described process, and the efficacy of halamine compounds in neutralizing biological and chemical agents, provide new applicability to biogenic and biomimetic materials.     

Effectiveness of a polyamide film releasing lactic acid on the growth of E. coli O157:H7, Enterobacteriaceae and Total Aerobic Count on vacuum-packed beef

The suitability of a polyamide 6 monolayer film containing lactic acid for use as an antimicrobial package for fresh beef cuts was studied. The release of lactic acid in an aqueous environment was immediate (within 1 h) and was from approx. 55 μg lactic acid/cm² film at 0–8 °C to approx. 67 μg lactic acid/cm² film at 12–20 °C. Beef was contaminated with an Escherichia coli O157:H7 isolate with known minimum inhibitory concentration against lactic acid (0.09% v/v), then wrapped with the lactic-acid polyamide film and vacuum packaged. During storage at 12 °C, the numbers of E. coli were 1 log unit lower than that of a control (untreated polyamide film) and decreased by an additional 1 log during storage for 14 days.     

Biological Availability and Preliminary Selenium Speciation in Selenium-Enriched Mycelium of Lentinula edodes (Berk.)

Our goal is to obtain a new food supplement — a chemopreventive preparation derived from selenium (Se)-enriched Lentinula edodes mycelium. In the present study the bioavailability of selenium from Se-enriched mycelium preparations was tested in vitro and in vivo. Three different preparations of selenated mycelium were compared: dried mycelium, lyophilized mycelium, and lyophilized-autolyzed mycelium. In vitro, estimated Se bioavailabilities were 60%, 82%, and 98%, respectively. In vivo bioavailability was determined in rats. As reference, sodium selenite and Se yeast formulations were used at an Se-equivalent dose. The pharmacokinetic data for tested mycelial preparations suggest a rapid but incomplete Se absorption, and rapid elimination, without risk of accumulation. The speciation of selenium in Se-enriched mycelial cultures was carried out by specific oxido-reduction reactions. For tested mycelium the main part of Se was in the 0 and IV oxidation states in inorganic form or combined in a lipid or carbohydrate structure, about 47% was in the –II state in Se-amino acids or in other undefined water- or alcohol soluble organic compounds. Differences in pharmacokinetic data for Se yeast and L. edodes mycelial formulations probably arise from differences in Se speciation. Our data suggest that formulations of selenized Lentinula edodes mycelium could be used in chemoprevention as food supplements.     

Molecular Docking Reveals the Binding Modes of Anticancer Alkylphospholipids and Lysophosphatidylcholine within the Catalytic Domain of Cytidine Triphosphate: Phosphocholine Cytidyltransferase

Alkylphospholipids are synthetic analogues of endogenous phosphatidylcholines with a remarkable ability: induce the selective apoptosis of exponentially growing tumor cells. One hypothesis concerning their mechanism of action is the inhibition of cytidine triphosphate:phosphocholine cytidyltransferase (CCT), which would significantly suppress the phosphatidylcholine biosynthesis to trigger apoptosis. Herein, homology modeling, docking simulations, and the analyses of molecular interaction fields are used to suggest the most probable binding modes of four alkylphospholipids (edelfosine, erucylphosphocholine, perifosine, and miltefosine) and lysophosphatidylcholine at the catalytic domain of human CCT. All compounds display bind modes in agreement with the corresponding groups found in the CCT substrate, phosphocholine, while their binding strengths are increased because of the interaction of the alkyl chains with hydrophobic residues from the M domain of the protein. Analyses of the geometry of the CCT binding‐site also suggest that small groups, such as benzyl/2‐phenylethyl ethers or equivalent heterocycles, could replace the O‐methyl group in edelfosine to yield even better inhibitors. It is believed this study can guide the development of new alkylphospholipids with an improved profile for the inhibition of phosphatidylcholine biosynthesis, a critical component for cell cycle progression that can be explored in cancer chemotherapy. Practical Applications: Studies focusing on the interactions between small ligands and their protein targets are decisive for the comprehension of how conformational changes in the macromolecular structure dictates the biological activity and, consequently, how they can be explored in drug discovery. Most of the current studies on alkylphospholipids focuses on their physicochemical interactions with cholesterol and sphingolipids in lipid rafts that, because of the variability and complexity of the membrane phases, hardly can provide structural data in the X‐ray crystallography assays necessary for molecular modeling studies. Therefore, by exploring the inhibition of human cytidine triphosphate:phosphocholine cytidyltransferase as an alternative and, probably, complementary hypothesis to the membrane rafts, a helpful strategy can be provided to overcome the clinical limitations of alkylphospholipids.     

Rhyme and reason: Analyses of dual retrieval cues.

If and only if each single cue uniquely defines its target, an independence model based on fragment theory can predict the strength of a combined dual cue from the strengths of its single cue components. If the single cues do not each uniquely define their target, no single monotonic function can predict the strength of the dual cue from its components; rather, what matters is the number of possible targets. The probability of generating a target word was .19 for rhyme cues, .14 for category cues, and .97 for rhyme-plus-category dual cues. Moreover, some pairs of cues had probabilities of producing their targets of .03 when used individually and 1.00 when used together, whereas other pairs had moderate probabilities individually and together. The results, which are interpreted in terms of multiple constraints limiting the number of responses, show why rhymes, which play a minimal role in laboratory studies of memory, are common in real-world mnemonics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure and properties of polyamides‐epoxidized elastomers blends

Blends of aliphatic polyamides (PA6, PA66, and PA12), containing 0–15 wt % nonepoxidized or epoxidized elastomers (statistical copolymer butadiene–styrene BS/EBS or linear block copolymer styrene–butadiene–styrene SBS/ESBS) were investigated. For PA6‐elastomer blends, taken as an example, it was shown that with increasing blending time, mechanical properties of blends increase, especially, if ESBS copolymer is used. It can be treated as an indirect sign of reactions between components. It was also found that in blends considerable changes of glass temperatures of components occur. Polyamides in blends with elastomers have smaller heats of fusion in comparison with virgin polyamides. It testifies to hindering of PA crystallization by elastomers. In some cases, significant shifts of melting points are also observed. Measurements of water contact angle show that all blends have very similar values of contact angles, which are lower than those of virgin polyamides. Elastomer content does not also affect the blend water uptake. However, it depends on the polyamide and elastomer type contrary to contact angle. Highest water uptake changes are observed in blends of PA66, especially for epoxidized elastomers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1872–1879, 2006     

A deeper understanding of the spontaneous derepression of the URA3 gene in MaV203 Saccharomyces cerevisiae and its implications for protein engineering and the reverse two-hybrid system

Within the field of protein-based biomaterials, the need exists for both covalent and oriented bioconjugation strategies for improved performance. Such bioconjugation reactions can be facilitated by engineering proteins with chemically activated amino acids at strategically chosen sites. The incorporation of these unnatural amino acids (uAAs) can be achieved by using the nonsense suppression technique. This requires an aminoacyl-tRNA-synthetase (aaRS) that exclusively recognizes the uAA and loads it to the corresponding tRNA. Appropriate (aaRS) mutants can be found through reverse engineering using the Saccharomyces cerevisiae strain MaV203. This strain contains a counterselectable, Gal4p-inducible SPAL10::URA3 fusion and deletions in the endogenous GAL80 and GAL4 genes. Therefore, it has been used extensively for the screening of aaRS mutant libraries. It is generally assumed that the SPAL10 promoter actively represses the URA3 gene in the absence of Gal4p, resulting in MaV203 cells with a Ura ⁻ phenotype. The current contribution reveals that in a small fraction of MaV203 cells, a basal expression of the URA3 gene occurs. The unexpected URA3 expression is reported for the first time, and the nature of the mutation causing this expression was identified as a spontaneous recessive mutation in a single gene of a protein involved in the repression of the SPAL10 promoter. The basal URA3 expression causes aaRS mutants to be missed, which affects the outcome of the library screening. It is demonstrated that the use of diploid cells can circumvent the MaV203 Ura⁺ phenotype, allowing for an optimization of S. cerevisiae library screening.