Introduction of functional groups onto polypropylene and polyethylene surfaces for immobilization of enzymes

Polypropylene and polyethylene surfaces are activated by introducing an active functional group through 1-fluoro-2 nitro-4-azidobenzene by UV irradiation. Horseradish peroxidase and glucose oxidase are immobilized onto the activated surfaces, simply by incubating the enzymes at 37 degrees C. When untreated surfaces are used, insignificant immobilization of the enzymes is observed.     

The kinesin-associated protein UNC-76 is required for axonal transport in the Drosophila nervous system

Kinesin-I is essential for the transport of membrane-bound organelles in neural and nonneural cells. However, the means by which kinesin interacts with its intracellular cargoes, and the means by which kinesin-cargo interactions are regulated in response to cellular transport requirements are not fully understood. The C terminus of the Drosophila kinesin heavy chain (KHC) was used in a two-hybrid screen of a Drosophila cDNA library to identify proteins that bind specifically to the kinesin tail domain. UNC-76 is an evolutionarily conserved cytosolic protein that binds to the tail domain of KHC in two-hybrid and copurification assays, indicating that kinesin and UNC-76 form a stable complex in vivo. Loss of Drosophila Unc-76 function results in locomotion and axonal transport defects reminiscent of the phenotypes observed in kinesin mutants, suggesting that UNC-76 is required for kinesin-dependent axonal transport. Unc-76 exhibits dosage-sensitive genetic relationships with Khc and Kinesin light chain mutations, further supporting the hypothesis that UNC-76 and kinesin-I work in a common transport pathway. Given the interaction of FEZ1, the mammalian homolog of UNC-76, with protein kinase Czeta, and the role of FEZ1 in axon outgrowth, we propose that UNC-76 helps integrate kinesin activity in response to transport requirements in axons.     

Exposure of Salmonella Enteritidis to chlorine or food preservatives decreases [corrected] susceptibility to antibiotics

Mutants of Salmonella Enteritidis selected following exposure to the sanitizer chlorine or to the preservatives sodium nitrite, sodium benzoate or acetic acid show resistance to multiple antibiotics (tetracycline, chloramphenicol, nalidixic acid, and ciprofloxacin). Complementation experiments with a functional marR restored antibiotic susceptibility of selected mutants to levels similar to wild-type strains, suggesting that mar mutation was responsible for resistance. The multiple antibiotic resistance (mar) operon is a global regulator controlling intrinsic resistance towards structurally and functionally unrelated antibiotics and other noxious agents. Mutants selected after exposure to an inducing agent maintained elevated antibiotic resistance after serial subculture in media void of the inducing agent. Results highlight the importance of monitoring the use of antimicrobial agents to ensure that concentrations capable of inactivating target pathogens are used.     

Structure of the 16S rRNA pseudouridine synthase RsuA bound to uracil and UMP

In Escherichia coli, the pseudouridine synthase RsuA catalyzes formation of pseudouridine (psi) at position 516 in 16S rRNA during assembly of the 30S ribosomal subunit. We have determined the crystal structure of RsuA bound to uracil at 2.0 A resolution and to uridine 5'-monophosphate (UMP) at 2.65 A resolution. RsuA consists of an N-terminal domain connected by an extended linker to the central and C-terminal domains. Uracil and UMP bind in a cleft between the central and C-terminal domains near the catalytic residue Asp 102. The N-terminal domain shows structural similarity to the ribosomal protein S4. Despite only 15% amino acid identity, the other two domains are structurally similar to those of the tRNA-specific psi-synthase TruA, including the position of the catalytic Asp. Our results suggest that all four families of pseudouridine synthases share the same fold of their catalytic domain(s) and uracil-binding site.     

Clofarabine in adult acute leukemias: clinical success and pharmacokinetics

Clofarabine is a deoxyadenosine analog synthesized with the intention of retaining the favorable mechanistic properties of fludarabine and cladribine while eliminating their undesirable characteristics. Phase I studies among 32 patients with acute leukemia defined a maximum tolerated dose (MTD) of 40 mg/m2/d given as a one hour infusion daily for 5 days. The dose limiting toxicity (DLT) was transient hepatotoxicity. In a phase II study, 62 patients with acute leukemias received clofarabine at the MTD over 1 hour daily for 5 days. Twenty patients (32%) achieved complete response (CR), 1 had a partial response (PR), and 9 had a CR but without platelet recovery (CRp), for an overall response rate of 48%. Pharmacokinetic studies in the phase I trial revealed marked heterogeneity in peak levels of clofarabine among patients at the end of infusion, however; there was a linear, dose dependent increase in clofarabine concentration in the plasma. Pharmacodynamically, at the MTD, DNA synthesis was inhibited by more than 80% at the end of infusion. In phase II studies, the relationship between the pharmacokinetics of clofarabine triphosphate accumulation and clinical response at the MTD was explored, revealing an accumulation advantage of the cytotoxic triphosphate in leukemia cells of responders. The circulating leukemia blasts of patients who respond to clofarabine therapy exhibited a favorable pharmacokinetic profile. In conclusion, clofarabine is an active agent in the treatment of acute leukemias and MDS, and cellular pharmacokinetics has prognostic significance.     

Capacitation and acrosome reaction in buffalo bull spermatozoa assessed by chlortetracycline and Pisum sativum agglutinin fluorescence assay

Studies on buffalo sperm capacitation have been limited because of the non-availability of a direct assay system. We describe two methods for detecting the acrosomal status of buffalo spermatozoa, namely chlortetracycline (CTC) fluorescence assay and Pisum sativum agglutinin (FITC-PSA) stain. We also test them under various treatment regimens and simultaneously standardize and calibrate them with transmission electron microscopy. An initial comparison of three physiological media, such as Krebs-Ringer bicarbonate buffer, Tyrode solution and Brackett & Oliphant medium (having different calcium concentrations and osmolality) used for studying the capacitation of buffalo spermatozoa and assessed by CTC, FITC-PSA, Giemsa stain and TEM, revealed Brackett & Oliphant medium to be marginally better than the other two media. When stained with chlortetracycline, three distinct fluorescent patterns were visible in buffalo spermatozoa under capacitating conditions. These were 'F' with fluorescence in the post acrosomal region characteristic of uncapacitated acrosome-intact cells; 'B' with fluorescence on the anterior portion of the sperm head and a dark band in the post-acrosomal region, characteristic of capacitated, acrosome intact cells and 'AR' with a fluorescent band on the posterior portion of the head, characteristic of acrosome-reacted cells. The FITC-PSA intensely labels the acrosomal region of acrosome intact buffalo sperm. Acrosome reacted sperms had diminished acrosomal labelling by both the probes used. Buffalo spermatozoa was not capacitated when calcium was either omitted from the medium or chelated with EGTA. In the presence of Ca2+ ionophore, A23187, 68% at 4 h and 85% at 8 h completed the acrosome reaction. Time course studies revealed a 4 h incubation period at 1.71 mM Ca2+ concentration to be necessary before transformation of 'F' to 'B' cells could take place. Spontaneous acrosome reaction induced at 6 and 8 h incubation of buffalo spermatozoa in KRB medium resulted in conversion of 'B' cells to 'AR' cells while 'F' cells remained unchanged. A simultaneous evaluation of acrosome intact and acrosome-reacted cells using FITC-PSA, Giemsa and TEM gave results similar to examination by CTC stain. Both the assays are rapid, reproducible, reliable and they detect an increase or decrease in physiological acrosome reactions. They thus can be used to study effects of calcium and prove to be good monitoring systems to identify buffalo sperm capacitation and acrosome reaction in individual buffalo bulls for fertility studies.     

Inter-laboratory comparison of numerical dosimetry for human exposure to 60 Hz electric and magnetic fields

In recent years, with the availability of high resolution models of the human body, numerical computations of induced electric fields and currents have been made in more than one laboratory for various exposure conditions. Despite the verification of computational methods, questions are often asked about the reliability of these data. In this paper, computational results from two laboratories that presented data in compatible formats are compared, supplemented with additional data from the third laboratory. Two exposures to uniform fields at 60 Hz are evaluated. The human body models used in the computations are different and so are the computation al methods and codes. There are some differences in the conductivity values used for some of the tissues, as well. The results of the comparison confirm that these data are reliable, as the overall agreement is reasonably good and the differences can be rationally explained. This comparison also underscores the importance of accurate data on the dielectric properties of tissues.     

Reconstructing voltage sensor-pore interaction from a fluorescence scan of a voltage-gated K+ channel

X-ray crystallography has made considerable recent progress in providing static structures of ion channels. Here we describe a complementary method-systematic fluorescence scanning-that reveals the structural dynamics of a channel. Local protein motion was measured from changes in the fluorescent intensity of a fluorophore attached at one of 37 positions in the pore domain and in the S4 voltage sensor of the Shaker K+ channel. The local rearrangements that accompany activation and slow inactivation were mapped onto the homologous structure of the KcsA channel and onto models of S4. The results place clear constraints on S4 location, voltage-dependent movement, and the mechanism of coupling of S4 motion to the operation of the slow inactivation gate in the pore domain.     

Freshwater ecotoxicity characterization factors for aluminum

Purpose

Aluminum (Al) is an abundant, non-essential element with complex geochemistry and aquatic toxicity. Considering its complex environmental behavior is critical for providing a reasonable estimate of its potential freshwater aquatic ecotoxicity in the context of Life Cycle Impact Assessment (LCIA).

Methods

Al characterization factors (CFs) are calculated using the following: (1) USEtox^? model version 2.1 for environmental fate, (2) MINEQL+ to estimate the distribution of Al between the solid phase precipitate and total dissolved Al, (3) WHAM 7 for Al speciation within the total dissolved phase, and (4) Biotic Ligand Model (BLM) and Free Ion Activity Model (FIAM) for ecotoxicity estimation for seven freshwater archetypes and default landscape properties for the European continent. The sensitivity of the CFs to aquatic chemistry parameters is calculated. New CFs are compared with Dong et al. (Chemosphere 112:26–33, 2014) and default CF calculated by USEtox 2.1.

Results and discussion

Al CFs vary over 5 orders of magnitude between the seven archetypes, with an arithmetic average CF_ave of 0.04 eq 1,4-DCB (recommended for use), geometric mean CF_geo of 0.0014 eq 1,4-DCB, and weighted average CF_wt of 0.026 eq 1,4-DCB. These values are lower (less toxic) than those for Cu, Ni, Zn, and Pb (with one exception). The effect factor (EF) contributed most to this variability followed by the bioavailability factor (BF), varying over 8 and 4 orders of magnitude, respectively. These revised CFs are 2–6 orders of magnitude lower than those presented by Dong et al. (Chemosphere 112:26–33, 2014) mainly because of consideration of Al precipitation.

Conclusions

Freshwater archetype-specific Al CFs for freshwater ecotoxicity that address the effect of Al speciation on bioavailability (BF) and ecotoxicity (EF) have been calculated, and a CF of 0.04 eq 1,4-DCB is recommended for use in generic LCA. For site-specific LCA, the choice of water chemistry and, in particular, pH, and consideration of metal precipitation could significantly influence results.

Practical implications

Incorporating estimates of metal speciation and its effect on aquatic toxicity is essential when conducting LCIA. Along with metal speciation estimates, the values derived from the definition of water chemistry parameters must also be included into LCIA. For site-generic assessments, we recommend using the arithmetic average of metal CFs. We also recommend using FIAM as a suitable alternative to BLM to estimate EF if the latter is not available. Consideration of metal speciation is essential for providing more realistic estimates of Al freshwater ecotoxicity in the context of LCIA.

     

Model membrane interaction and DNA-binding of antimicrobial peptide Lasioglossin II derived from bee venom

Lasioglossins, a new family of antimicrobial peptide, have been shown to have strong antimicrobial activity with low haemo-lytic and mast cell degranulation activity, and exhibit cytotoxic activity against various cancer cells in vitro. In order to understand the active conformation of these pentadecapeptides in membranes, we have studied the interaction of Lasioglossin II (LL-II), one of the members of Lasioglossins family with membrane mimetic micelle Dodecylphosphocholine (DPC) by fluorescence, Circular Dichroism (CD) and two dimensional (2D) ¹H NMR spectroscopy. Fluorescence experiments provide evidence of interaction of the N-terminal tryptophan residue of LL-II with the hydrophobic core of DPC micelle. CD results show an extended chain conformation of LL-II in water which is converted to a partial helical conformation in the presence of DPC micelle. Moreover we have determined the first three-dimensional NMR structure of LL-II bound to DPC micelle with rmsd of 0.36 Å. The solution structure of LL-II shows hydrophobic and hydrophilic core formation in peptide pointing towards different direction in the presence of DPC. This amphipathic structure may allow this peptide to penetrate deeply into the interfacial region of negatively charged membranes and leading to local membrane destabilization. Further we have elucidated the DNA binding ability of LL-II by agarose gel retardation and fluorescence quenching experiments.