Effects of prolonged exposure to moderate static magnetic field and its synergistic effects with alkaline pH on Enterococcus faecalis.

Static magnetic field (SMF) has been shown to biologically affect various microorganisms, but its effects on Enterococcus faecalis, which is associated with multiple dental infections, have not been reported yet. Besides, Enterococcus faecalis was found to be resistant to the alkaline environment provided by a major dental antimicrobial, calcium hydroxide. Therefore, the antibacterial activity of prolonged exposure to moderate SMF (170 mT) and its possible synergistic activity with alkaline pH (pH = 9) were evaluated in the study. The ability to form a biofilm under these conditions was examined by crystal violet assay. Real-time quantitative PCR was performed to evaluate the relative expression of stress (dnaK and groEL) and virulence (efaA, ace, gelE and fsrC) related genes. As the results indicated, cell proliferation was inhibited after 120 h of SMF exposure. What's more, the combined treatment of SMF and alkaline pH showed significantly improved antimicrobial action when compared to single SMF and alkaline pH treatment for more than 24 h and 72 h respectively. However, the ability to form a biofilm was also enhanced under SMF and alkaline pH treatments. SMF can induce stress response by up-regulating the expression of dnaK and elevate virulence gene expression (efaA and ace). These responses were more significant and more genes were up-regulated including groEL, gelE and fsrC when exposed to SMF and alkaline pH simultaneously. Hence, combination of SMF and alkaline pH could be a promising disinfection strategy in dental area and other areas associated with Enterococcus faecalis infections.

Infrared Laser Activation of Soluble and Membrane Protein Assemblies in the Gas Phase.

Collision-induced dissociation (CID) is the dominant method for probing intact macromolecular complexes in the gas phase by means of mass spectrometry (MS). The energy obtained from collisional activation is dependent on the charge state of the ion and the pressures and potentials within the instrument: these factors limit CID capability. Activation by infrared (IR) laser radiation offers an attractive alternative as the radiation energy absorbed by the ions is charge-state-independent and the intensity and time scale of activation is controlled by a laser source external to the mass spectrometer. Here we implement and apply IR activation, in different irradiation regimes, to study both soluble and membrane protein assemblies. We show that IR activation using high-intensity pulsed lasers is faster than collisional and radiative cooling and requires much lower energy than continuous IR irradiation. We demonstrate that IR activation is an effective means for studying membrane protein assemblies, and liberate an intact V-type ATPase complex from detergent micelles, a result that cannot be achieved by means of CID using standard collision energies. Notably, we find that IR activation can be sufficiently soft to retain specific lipids bound to the complex. We further demonstrate that, by applying a combination of collisional activation, mass selection, and IR activation of the liberated complex, we can elucidate subunit stoichiometry and the masses of specifically bound lipids in a single MS experiment.

Effect of gamma radiation on heat shock protein expression of four foodborne pathogens.

AIMS: The effects of gamma radiation on three heat shock proteins (Hsps) (GroEL, DnaK and GroES) synthesis in two Gram-negative (Escherichia coli and Salmonella serotype Typhimurium) and two Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria were investigated. METHODS AND RESULTS: The bacterial strains were treated with three radiation doses to induce cell damage, to obtain a viable but nonculturable state, and to cause cell death. Western blot analysis and quantification of Hsps in bacteria were performed immediately after irradiation treatment. In the four foodborne pathogens, GroEL was strongly induced by gamma rays in a dose-dependent manner, confirming the involvement of this protein in the cellular response to the stress generated by ionizing radiation. In addition, it was found that E. coli exposed to gamma radiation showed a significantly induction of DnaK and GroES proteins when compared with nonirradiated bacteria, whereas a GroES slight induction and a DnaK inhibition were observed in Salm. Typhimurium. CONCLUSIONS: The gamma rays influence the synthesis of Hsps in foodborne pathogen in a way that critically depends on the radiation dose. SIGNIFICANCE AND IMPACT OF THE STUDY: The study of stress response to several radiation doses was undertaken to elucidate how bacteria can survive in harsh conditions and cope with gamma radiation used to control foodborne pathogens and to characterize their adaptative response to this treatment.

Semibiological molecular machine with an implemented "AND" logic gate for regulation of protein folding.

A semibiological molecular machine with an implemented "AND" logic gate was developed, which was capable of controlling the folding process of proteins in response to ATP and light as input stimuli. The molecular design made use of a genetically engineered chaperonin GroEL bearing, at both entrance parts of its cylindrical cavity, cysteine residues, which were functionalized by an azobenzene derivative to construct photoresponsive mechanical gates (azo-GroEL). This engineered chaperonin trapped denatured green fluorescent protein (GFP(denat)) and prohibited its refolding. However, when hosting azo-GroEL detected ATP (input stimulus 1) and UV light (input stimulus 2) at the same time, it quickly released GFP(denat) to allow its refolding. In contrast, reception of either input stimulus 1 or 2 resulted in only very slow or no substantial refolding of GFP(denat). Implementation of such "AND" logic gate mechanisms in mechanically driven biomolecular systems is an important step toward the design of secured drug delivery systems.

Response of human lymphocytes to low gamma ray doses

Linfocitos humanos fueron irradiados en un campo de radiación gamma de baja intensidad para determinar la expresión de las proteínas de choque calórico en función de la dosis. Los linfocitos fueron obtenidos de individuos cuyo trabajo los identifica como ocupacionalmente expuesto y no ocupacionalmente expuestos. La identidad de las proteínas se realizó utilizando anticuerpos contra las proteínas Hsp25, Hsp60, Hsp70 y Hsp90. De éstas, solamente la proteína hsp70 fue detectada antes y después de la irradiación. Los linfocitos del personal ocupacionalmente expuesto y no ocupacionalmente expuesto expresaron, antes y después de la irradiación, solamente la proteína Hsp70. La cantidad de proteína resultó directamente proporcional al tiempo de irradiación. Después de una dosis gamma de 70.5 mGy, los linfocitos del individuo ocupacionalmente expuesto expresaron una mayor cantidad de proteína Hsp70 que la expresada por los linfocitos del personal no ocupacionalmente expuesto. Este hecho es indicio de que el individuo ocupacionalmente expuesto tiene una mayor tolerancia a los rayos gamma (gamma-tolerancia), inducida por un proceso de adaptación generada por su condición laboral

Photoincorporation of 4,4'-bis(1-anilino-8-naphthalenesulfonic acid) into the apical domain of GroEL: specific information from a nonspecific probe.

The use of noncovalent hydrophobic probes such as bis-ANS has become increasingly popular in gaining structural information about protein structure and conformation. While these probes have provided rich information about protein conformation, specific information has been limited. In this report, we extend the usefulness of the probe bis-ANS by showing that it can be covalently photoincorporated into various proteins. Using the chaperonin GroEL, we have shown that it is possible to locate important hydrophobic surfaces through photoincorporation and peptide sequencing. It has been proposed that hydrophobic surfaces on the chaperonin may be responsible for the binding of unfolded polypeptides. We show here that photoincorporation of bis-ANS is able to locate a distinct hydrophobic surface on GroEL. Incorporation of the bis-ANS occurs within a 45 residue fragment of the monomer near the middle of the primary sequence. Interestingly, photoincorporation occurs within this fragment in both tetradecamers and assembly-competent monomers. From the three-dimensional structure of GroEL, this region maps to the apical domain (residues 191-376), which has been implicated in polypeptide binding [Fenton, W. A., Kashi, Y., Furtak, K., & Horwich, A. L. (1994) Nature 371, 614-619]. In addition, the fluorescent properties of the probe are retained including the excitation and emission maxima and the sensitivity to the polarity of its environment. These results suggest that photoincorporated bis-ANS may be a useful probe for protein structure and dynamics.