Phase Of Inactivation Research Articles

Determination of strain variability and kinetics of food-associated microorganisms following ultrasound treatment

Ultrasound is a promising emerging technology known for its antimicrobial efficacy. However, existing studies have not fully addressed the impact of strain variability and inactivation kinetics on US efficacy. Ten strains of Listeria monocytogenes, Lactiplantibacillus plantarum, Saccharomyces cerevisiae and Escherichia coli were exposed to US treatment (26 kHz, 200 mL, 100 % amplitude, 200 W, 65–71 W/cm2) under dynamic conditions to investigate their resistance profile. Furthermore, the inactivation kinetics of selected resistant/sensitive strains were assessed. The result showed significant intra-species variability in resistance (p < 0.05) for the four target microorganisms evaluated in this study. L6 and NCTC 10357 were the most resistant and sensitive L. monocytogenes strains respectively, having a reduction difference of ∼3.4 log CFU/mL. Regarding L. plantarum, FBR04 emerged as the most resistant strain (4.4 log reduction), while E. coli FAM21845, FAM21805 and FAM21843 (∼2 log reduction) emerged as the most resistant strains. On the other hand, the most resistant strains of S. cerevisiae were CBS 1544, AD 1890 and 077.0001 (<1 log reduction) while S. cerevisiae AD 2913, 028.0404 and 028.0315 were the most sensitive (>5 log reduction). The survival curves of most of the strains exhibited an initial phase of insignificant microbial inactivation followed by a relatively fast log-linear inactivation period. The estimated D-value showed that L. monocytogenes strains exhibited higher resistance to US treatment than any other species, while other species displayed comparable resistance. The findings on strain variability resistance and inactivation kinetics following US treatment are essential for food safety and will pave the way for further research on microbial response to US stress, risk assessment and optimisation studies.

Enhancing monoclonal antibody stability during protein a chromatography using 2-methyl imidazolium dihydrogen phosphate

This study investigates the impact of 2-methyl imidazolium dihydrogen phosphate (2-MIDHP) on monoclonal antibody (mAb) aggregation during the Protein A purification stage, at a low pH (pH 3.0), and the viral inactivation phase. Size-exclusion high-performance liquid chromatography (SE-HPLC) and dynamic light scattering (DLS) were used to assess the mAb aggregation. Additionally, the influence of 2-MIDHP on mAb recovery, host cell protein (HCP) clearance, and Protein A leaching was investigated. Thermal stability of mAb, eluted in buffers containing 5 % to 25 % 2-MIDHP was analysed, using differential scanning calorimetry (DSC). Structural insights were obtained via circular dichroism (CD) and fluorescence spectroscopy. Our findings indicated that 2-MIDHP exerted a concentration-dependent protective effect against mAb aggregation, at the pH of 3.0. As the concentration of 2-MIDHP was increased from 0 % to 25 %, the aggregation was significantly reduced from 3.8 ± 0.01 % to 0.56 ± 0.002 %, as analysed by SE-HPLC. Addition of 2-MIDHP did not significantly impact the mAb recovery, HCP clearance, or Protein A leaching. DSC data supported these results, with higher 2-MIDHP concentrations leading to increased melting temperatures of mAb. CD and fluorescence spectroscopy revealed no significant changes in the secondary structure or aromatic residue environment in 2-MIDHP-treated samples, despite the observed reduction in aggregation. The results suggested that 2-MIDHP mitigated mAb aggregation during Protein A purification, possibly by stabilizing the protein structure under acidic stress conditions. These findings offer valuable insights for improving the robustness of mAb purification processes, enhancing product quality and yield.

Inventory and kinematics of active and transitional rock glaciers in the Southern Alps of New Zealand from Sentinel-1 InSAR

ABSTRACT In this study, we inventoried and mapped the active and transitional rock glaciers in the central part of the Southern Alps, New Zealand, using Sentinel-1 InSAR (interferometric synthetic aperture radar) data. We used forty-three interferograms acquired between 2015 and 2019 with time intervals between six days and two years along with orthoimage analyses. A total of 123 rock glaciers were identified, of which 40 are active; that is, displaying velocities higher than 10 cm/yr. The remaining landforms are considered transitional. Among the complete sample of rock glaciers inventoried, 9 may also be interpreted as debris-covered glacierets. The number of inventoried landforms is low compared to what is observed in other similar mountain ranges, such as the European Alps. We explain this by the reduced vertical extent of the periglacial belt and the generally steep topography often not favorable for rock glacier development. Additionally, the motion rates appear relatively low. We hypothesize that a mean annual air temperature at the rock glacier locations well above 0°C is the main reason for this. These conditions may have resulted in significant ground ice melt. Rock glaciers in the Southern Alps are thus in an inactivation phase, which is expressed by typical morphologies such as stable fronts.

Abstract 11832: Activated Cardiomyocytes in the Cell Cycle Promote Cardiac Engraftment

Rationale: The only treatment for drug-resistant heart failure is heart transplantation, however, it has problems such as donor shortages and rejection. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-cardiomyocytes) are promising sources of regenerative medicine that can solve these problems. The engraftment potential of hiPSC-cardiomyocytes following the transplantation into the host heart should be improved to realize this therapy. Objective: We aim to discover a compound to enhance the engraftment of hiPSC-cardiomyocytes following the cell transplantation into the damaged heart. We also aim to realize a larger graft size and recover cardiac function. Methods and Results: We established an iPSC line constitutively expressing Fluorescent Ubiquitination-based Cell Cycle Indicator (FUCCI), which can show the cell cycle phase in real-time. We compared the engraftment capacity of hiPSC-cardiomyocytes in between the S/G2/M (activation) phase and G0/G1 (inactivation) phase for three months after transplantation, finding cell cycle activated hiPSC-cardiomyocytes showed significantly higher engraftment efficiency than those in inactivated. We, thus, conducted the screening to find cell-cycle activating compounds in the hiPSC-cardiomyocytes. The screening identified some candidates from more than 4000 compounds, and we focused on the most effective compound (CCA-1). An EdU assay and cell number count demonstrated the activation of proliferative capacity by CCA-1. Moreover, genetic analysis revealed a group of genes related to CCA-1-induced cell cycle activation. Finally, using in vivo bioluminescent imaging, we confirmed that CCA-1 treated hiPSC-cardiomyocytes showed enhanced graft size after transplantation into mice ischemic heart. Conclusions: This study highlights the effectiveness of the FUCCI system to analyze the cell cycle status in hiPSC-cardiomyocytes, and the cell cycle activation by CCA-1 is the efficient strategy to increase the graft size following the cell transplantation into the damaged heart.

Recordings of action potentials, charge movements, and sarcoplasmic reticulum Ca2+ release in isolated adult zebrafish fast skeletal muscle fibers reveals very fast kinetics of excitation–contraction coupling

The zebrafish has emerged as a very relevant animal model to decipher the pathophysiology of human muscle disorders. However, the vast majority of studies on zebrafish skeletal muscle have investigated genetic, histological, and molecular aspects, but functional approaches at the cellular level, especially in the field of excitation-contraction (EC) coupling, are scarcer and generally limited to cultured myotubes or fibers from embryonic zebrafish. Considering that zebrafish undergoes profound metamorphosis during transition from larval to adult stage and that number of muscle pathologies come up at ages far beyond embryonic stages, there is an actual need to investigate EC coupling in fully differentiated zebrafish skeletal muscle. In the present study, we were able to implement current and voltage clamp combined with intracellular Ca2+ measurements using the intracellularly loaded Ca2+ dye indo-1 in enzymatically isolated fast skeletal muscle fibers from 1-yr old zebrafish. Recording of action potentials (AP) in current-clamp conditions revealed very fast kinetics of the repolarization phase of AP. Measurements of intramembrane charge movements in voltage-clamp conditions showed that charge movement density was half that measured in mammalian fibers, but they displayed much faster kinetics. Ca2+ transients elicited by depolarization displayed a voltage-dependent phase of activation and voltage- and time-dependent phase of inactivation. Recording of Ca2+ signals elicited by trains of AP at different rates in current-clamp conditions indicated that Ca2+ signals fused at very high stimulation frequencies with no sign of Ca2+ signal decay for the entire 0.5 s duration of the stimulation, giving evidence that fibers were still able to generate AP and the sarcoplasmic reticulum to release Ca2+ with stimulation rates as high as 200 Hz. These data indicate that adult zebrafish fast skeletal muscle fibers exhibit strikingly fast kinetics of EC coupling from AP firing to charge movements and sarcoplasmic reticulum Ca2+ release.

Kinetics and Mechanisms of Virus Inactivation by Chlorine Dioxide in Water Treatment: A Review.

Chlorine dioxide (ClO2), an alternative disinfectant to chlorine, has been widely applied in water and wastewater disinfection. This paper aims at presenting an overview of the inactivation kinetics and mechanisms of ClO2 with viruses. The inactivation efficiencies vary greatly among different virus species. The inactivation rates for different serotypes within a family of viruses can differ by over 284%. Generally, to achieve a 4-log removal, the exposure doses, also being referred to as Ct values (mutiplying the concentration of ClO2 and contact time) vary in the range of 0.06–10 mg L−1 min. Inactivation kinetics of viruses show two phases: an initial rapid inactivation phase followed by a tailing phase. Inactivation rates of viruses increase as pH or temperature increases, but show different trends with increasing concentrations of dissolved organic matter (DOM). Both damages in viral proteins and in the 5′ noncoding region within the genome contribute to virus inactivation upon ClO2 disinfection.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00128-021-03137-3.

Is It Possible to Restore a Heavily Polluted, Shallow, Urban Lake?

The research was carried out on Karczemne Lake, a water reservoir located in Kartuzy (northern Poland, Pomeranian Lake District). Monitoring of the water and bottom sediment of Karczemne Lake showed a very high level of contamination of the reservoir by a long-term inflow of untreated municipal sewage. The trophic status index of total phosphorus (TP) was unusually high at 101, and the TP content in the bottom sediments—31 mg g−1 (dry weight)—was the highest value recorded worldwide in a lake. Based on the monitoring results, to achieve constant improvement of the water quality, we recommend a completely new, safe and economically justified method of bottom sediment removal and management. A very important aspect of this method is the prevention of uncontrolled sewage discharge back into the lake basin. Removed sediment with interstitial water will be pumped through a pipeline and transported to a sewage treatment plant. In the sediment mining field in which the sludge will be removed, the first phase of phosphorus inactivation will be carried out to chemically precipitate pollutants distributed in the water column as a result of sediment resuspension. After the deepening of the entire lake basin, the method of phosphorus inactivation will be carried out on the entire surface of the lake as the next stage of restoration. A supporting activity will be biomanipulation. Before the restoration is started, the municipal sewerage system will be modernized.

Thermal and ultraviolet-c inactivation of Salmonella enterica in cold-pressed virgin coconut oil

Virgin Coconut Oil (VCO) consumption as functional food has recently become popular together with increasing evidence of its health benefits. However, cold-pressed VCO types are highly manually produced without the application of kill step to ensure safety from possible pathogenic contaminants. The study therefore determined the inactivation behavior and kinetic parameters of Salmonella enterica in VCO subjected to mild heat and ultraviolet-c (UV–C) irradiation. When exposed to 50–70 °C, S. enterica exhibited a biphasic inactivation behavior with initial, logarithmic linear population decline of 2.07–2.39 log CFU/mL. An inactivation tail followed where minimal population changes took place. Total inactivated cells ranged from 2.28 to 2.35 log CFU/mL, which were achieved from 2. o to 100 min. Similar behavior was observed in UV-C-irradiated VCO at surface irradiance of 1.25–3.99 mW/cm2. Population decline in the log-linear inactivation phase ranged from 2.59 to 4.00 log CFU/mL, achieved after 0.33–1.20 min. After irradiation for 2.0 min, the total inactivated population ranged from 2.68 to 4.17 log CFU/mL. Complete elimination of S. enterica was not observed in any of the highly contaminated VCOs. These results provide baseline information for the establishment of pasteurization processes to achieve VCO safety.

Antiviral activity of the sea cucumber tegument extract (Pattalus mollis) on human rotavirus A (RVA)

The antiviral effect against RVA in cell culture was evaluated by using an aqueous extract of Patallus mollis sea cucumber, applying the titration methodology. This technique is used to measures the ability of the extract dilutions to inhibit the cytopathic effect (CPE) of the virus, expressed as percentage of inhibition (IP). The mean extract cytotoxic concentration (CC50) used in the antiviral assay was 27,042.10 μg/mL and the PI of the antiviral activity extract was greater than 99.9% for each concentration. To determine the viral action mode, the cells were previously treated with the extracts in different stages during the viral infection cycle. The result analysis suggests that the extract inhibits 99% of the virus during the absorption and viral inactivation phase. These results show the P. mollis extract has a remarkable antiviral effect against the RVA in cell culture. So that, it is crucial to investigate its action mechanisms.

The citrus flavanone hesperetin preferentially inhibits slow-inactivating currents of a long QT syndrome type 3 syndrome Na+ channel mutation.

The citrus flavanone hesperetin has been proposed for the treatment of several human pathologies, but its cardiovascular actions remain largely unexplored. Here, we evaluated the effect of hesperetin on cardiac electrical and contractile activities, on aortic contraction, on the wild-type voltage-gated NaV 1.5 channel, and on a channel mutant (R1623Q) associated with lethal ventricular arrhythmias in the long QT syndrome type 3 (LQT3). We used cardiac surface ECG and contraction force recordings to evaluate the effects of hesperetin in rat isolated hearts and aortic rings. Whole-cell patch clamp was used to record NaV 1.5 currents (INa ) in rat ventricular cardiomyocytes and in HEK293T cells expressing hNaV 1.5 wild-type or mutant channels. Hesperetin increased the QRS interval and heart rate and decreased the corrected QT interval and the cardiac and aortic contraction forces at concentrations equal or higher than 30μmol·L-1 . Hesperetin blocked rat and human NaV 1.5 channels with an effective inhibitory concentration of ≈100μmol·L-1 . This inhibition was enhanced at depolarized holding potentials and higher stimulation frequency and was reduced by the disruption of the binding site for local anaesthetics. Hesperetin increased the rate of inactivation and preferentially inhibited INa during the slow inactivation phase, these effects being more pronounced in the R1623Q mutant. Hesperetin preferentially inhibits the slow inactivation phase of INa , more markedly in the mutant R1623Q. Hesperetin could be used as a template to develop drugs against lethal cardiac arrhythmias in LQT3.

Approaching to the Molecular Mechanism of the Fast Inactivation of Calcium Selective TRP Channels

TRPV5 and TRPV6 are inwardly rectifying calcium selective channels, considered as gatekeepers of epithelial calcium transport and key elements for calcium homeostasis. Intracellular calcium exert a negative control over the activity of these channels. In mammals, TRPV6 channels show a characteristic fast calcium-dependent inactivation phase, that is absent in TRPV5 channels at physiological conditions. It has been evidenced that the intracellular loop located between the transmembrane segments (TM) S2-S3 and residues downstream the TM S6 are involved in the mechanism of fast inactivation, however the molecular mechanism driving fast inactivation is not known. In the present study we establish a structural-functional correlation of this process. By means of electrophysiological recordings we identified a set of conserved residues at the Helix-Loop-Helix (HLH) domain that modulates the inactivation phenotype. Molecular dynamics simulations suggest that the inactivation phenotype can be explained by specific conformational changes induced by calcium coordination to a structural triad formed by the HLH domain, the intracellular connector between TM S2-S3, and the TRP helix.

MS2 coliphage and E. coli UVB inactivation rates in optically clear water: dose, dose rate and temperature dependence.

Natural ultraviolet irradiance disinfection is known to play a significant role in both natural wastewater treatment systems and drinking water disinfection processes, while the influence of ultraviolet B (UVB) delivering method on sunlight disinfection outcome is still unclear. This study aims to determine the effects of environmentally relevant temperatures, UVB doses (J m-2) and dose rates (W m-2) on the inactivation and log reduction values (LRVs) of the F-RNA coliphage MS2 and Escherichia coli in optically clear water. E. coli and MS2 were separately incubated and irradiated at five different doses of UVB light that delivered using six UVB dose rates. The results of the study demonstrate that the UVB dose delivering method (combination of dose rate and exposure time) influences inactivation and LRVs of E. coli and MS2 at all UVB doses investigated (up to seven-fold difference). Two phases were identified within the UVB dose rate, UVB inactivation or LRV curves for both organisms; a UVB dose rate limited inactivation phase and a dose rate saturation inactivation phase. The results contribute to a better understanding of UVB disinfection in the environment and natural wastewater treatment systems, potentially improving the design and operation of high rate algal ponds.

Molecular dissection of multiphase inactivation of the bacterial sodium channel NaVAb.

Homotetrameric bacterial voltage-gated sodium channels share major biophysical features with their more complex eukaryotic counterparts, including a slow-inactivation mechanism that reduces ion-conductance activity during prolonged depolarization through conformational changes in the pore. The bacterial sodium channel NaVAb activates at very negative membrane potentials and inactivates through a multiphase slow-inactivation mechanism. Early voltage-dependent inactivation during one depolarization is followed by late use-dependent inactivation during repetitive depolarization. Mutations that change the molecular volume of Thr206 in the pore-lining S6 segment can enhance or strongly block early voltage-dependent inactivation, suggesting that this residue serves as a molecular hub controlling the coupling of activation to inactivation. In contrast, truncation of the C-terminal tail enhances the early phase of inactivation yet completely blocks late use-dependent inactivation. Determination of the structure of a C-terminal tail truncation mutant and molecular modeling of conformational changes at Thr206 and the S6 activation gate led to a two-step model of these gating processes. First, bending of the S6 segment, local protein interactions dependent on the size of Thr206, and exchange of hydrogen-bonding partners at the level of Thr206 trigger pore opening followed by the early phase of voltage-dependent inactivation. Thereafter, conformational changes in the C-terminal tail lead to late use-dependent inactivation. These results have important implications for the sequence of conformational changes that lead to multiphase inactivation of NaVAb and other sodium channels.

Assessment of thin-film photocatalysis inactivation of different bacterial indicators and effect on their antibiotic resistance profile

The presence of bacterial pathogens in water bodies, alongside their growing antibiotic resistance, endanger access to freshwater sources and necessitate their successful inactivation with a proper disinfection technology. In the present study, a parallel plate reactor (PPL) with immobilized photocatalyst was used as a disinfection system for the inactivation of two bacterial indicators (Escherichia coli and Enterococcus faecalis) in aqueous samples. Experiments were carried out at parallel plate reactor configuration (PPL) operated in recycling batch mode. Titanium Tetraisopropoxide (TTIP) based thin-film coated photocatalyst surfaces were used and assessed operations parameters were; pH, initial bacteria concentration, source and type of bacteria. The effect of the photocatalytic process on antibiotic resistance profile of target bacteria was also investigated as it may serve as a pioneering step in the field of well-established and modern disinfection method development, without causing proliferation of antibiotic resistance. The observed courses of bacterial inactivation and the final disinfection rates point out diversity in the level of interaction between different type/source of bacteria and photocatalyst of concern. According to the results, a stationary phase of bacteria inactivation proceeded with a rapid and efficient one for the case of E. faecalis (99% removal after 180 min and 99.9% removal after 240 min), while the trend for E. coli is more likely to be described as extended along the process time. Among the tested antibiotics, E. coli Minimum inhibition concentration (MIC) values for beta-lactam, macrolide and aminoglycoside groups were considerably altered (namely Ampicillin, Cefaclor, Clarithromycin - Erythromycin and Amikacin, respectively). PC oxidation was approved to be efficient on bacterial inactivation and trigger alterations on resistance behaviour of E.coli and Enterococcus sp. strains.

Differences in the synchronization of alpha oscillations between anterior and posterior brain regions

Alpha oscillations generated in the human brain have long been investigated in neuroscience. Synchronized oscillatory activities of numerous neural oscillators are thought to underlie alpha oscillations. The amplitude of alpha oscillations reflects the degree of synchronization, which is often modulated through alpha activation and inactivation, for example, in event-related synchronization and desynchronization. The range of synchronization can be estimated using the similarity between neighboring alpha oscillations. Yet, little is known about how the synchronization range of alpha oscillations varies with alpha activation/inactivation over different brain regions. To examine this, we recorded human electroencephalography (EEG) during different tasks used to modulate alpha oscillations. We found that the synchronization range of posterior alpha oscillations was reduced in the activation phase compared to that in the inactivation phase. In contrast, the synchronization range of anterior alpha oscillations was enhanced in the activation phase compared to that in the inactivation phase. The results imply that the mechanisms generating anterior and posterior alpha oscillations may be different.

Modeling squid axon Na+ channel by a nucleation and growth kinetic mechanism

A kinetic model accounting for all salient features of the Na+ channel of the squid giant axon is provided. The model furnishes explanations for the Cole-Moore-like effect, the rising phase of the ON gating current and the slow ‘intermediate component’ of its decaying phase, as well as the gating charge immobilization. Experimental ON ionic currents are semi-quantitatively simulated by the use of only three free parameters, upon assuming that the Na+ channel opening proceeds along with the stepwise aggregation of its four domains, while they are moving their gating charge outward under depolarizing conditions. The inactivation phase of the ON ionic current is interpreted by a progressive electrostatic attraction between the positively charged ‘hinged lid’ containing the hydrophobic IFM triad and its receptor inside the channel pore, as the stepwise outward movement of the S4 segments of the Na+ channel progressively increases the negative charge attracting the triad to its receptor. The Na+ channel closing is assumed to proceed by repolarization-induced disaggregation of its domains, accompanied by inward movement of their gating charge. The phenomenon of ‘gating charge immobilization’ can be explained by assuming that gradual structural changes of the receptor over the time course of depolarization strengthen the interaction between the IFM triad and its receptor, causing a slow release of the gating charge during the subsequent repolarization.

Evolutionary Variations in HLH Domain Modulate the Fast Inactivation Phase in Calcium Selective TRP Channels

Evolutionary Variations in HLH Domain Modulate the Fast Inactivation Phase in Calcium Selective TRP Channels

Rufinamide for the treatment of Lennox-Gastaut syndrome: evidence from clinical trials and clinical practice.

Rufinamide was granted orphan drug status in 2004 for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in patients aged ≥4 years, and was subsequently approved for this indication in several countries, including Europe and the United States. Structurally unrelated to other antiepileptic drugs, rufinamide is thought to act primarily by prolonging the inactivation phase of voltage-gated sodium channels. Rufinamide was approved on the basis of an international, randomised, placebo-controlled Phase III trial, conducted in 138 patients with Lennox-Gastaut syndrome, which demonstrated its favourable tolerability profile and efficacy in significantly reducing the frequency of drop attacks and total seizures, compared with placebo. The effectiveness and safety/tolerability of rufinamide in treating seizures associated with Lennox-Gastaut syndrome have subsequently been confirmed in several other clinical trials and long-term extension studies. These findings are supported by 'real-world' data from a series of clinical practice studies conducted in Europe, the United States, and Korea. Rufinamide has been shown to be effective and generally well tolerated in children as young as one year and in adults. It is particularly effective as treatment for drop attacks and generalised tonic-clonic seizures, and it has been suggested that it might be preferred over other antiepileptic drugs as a second-line treatment for Lennox-Gastaut syndrome when drop attacks are frequent. The most common side effects of rufinamide treatment include somnolence, headache, dizziness, nausea, vomiting, and fatigue. No new or unexpected safety signals have emerged following long-term treatment with rufinamide, either in clinical trials or in clinical practice.

Elimination of Salmonella enterica on common stainless steel food contact surfaces using UV-C and atmospheric pressure plasma jet

This study aimed to evaluate the efficacy of ultraviolet-C irradiation and atmospheric pressure plasma jet treatment as inactivation methods of Salmonella spp. on stainless steel surfaces commonly used as food contact surfaces. Two types of stainless steel namely 304 and 316, were used as test surfaces with each type having three different finishes: 2B, Hair line (HL), and Mirror (MR). A cocktail of 7 serovars of S. enterica at mid stationary phase (17 h) cells were allowed to adhere onto the surfaces (4h) prior to UV-C and plasma treatment. Results showed that the test organism exhibited a biphasic UV-C inactivation composed of a fast log linear inactivation phase followed by a slower inactivation tail on all test surfaces. The D values calculated from the faster log linear inactivation phase ranged from 2.54 (316 2B and 316 HL) to 4.31 s (304 2B). The maximum population reduction calculated before the inactivation tail ranged from 3.32 (316 HL) to 4.97 log CFU/in2 (304 MR). Plasma treatment of metal surfaces resulted in abrupt increase in surface temperature, reaching up to 180 °C within 15 s of treatment, and led to log linear inactivation in all surfaces treated with atmospheric plasma jet. The D values ranged from 2.66 (304 2B) to 3.43 s (316 MR). Both metal type and surface finish were observed not to affect the efficacies of UV-C inactivation and atmospheric pressure plasma jet treatment. The results obtained in the study demonstrated the potential of the tested physical treatments as alternatives to commonly used food contact surface chemical sanitation protocols.

Control of Slow, Use Dependent Inactivation of NaVAb by its C Terminal Tail

Bacterial voltage-gated sodium channels are composed of four identical subunits. They share major biophysical features with eukaryotic counterparts. Crystallization of full-length bacterial sodium channels (Payandeh et al. 2011, 2012; Zhang et al. 2012) makes them invaluable models for studying the structural basis of ion conductance, activation, inactivation, and drug interaction. Mammalian sodium channels have two main types of inactivation: fast inactivation on the order of milliseconds, which is mediated by the IFM motif in the intracellular loop between domains III and IV; and slow inactivation on the order of hundreds of milliseconds to seconds, which is believed to occur through pore collapse. The bacterial sodium channel NavAb activates at very negative membrane potentials, and it has a late use-dependent phase of slow inactivation that reverses very slowly (Gamal El-Din et al. 2013). We studied the effect of the NavAb C-terminal cytoplasmic domain on use-dependent slow inactivation. Deletion of 40 residues of the cytoplasmic tail (α40) abolished late use-dependent inactivation. Progressively smaller deletions to yield α28, α10, α7, and α3 caused graded effects. However, deletion of only 10 residues was sufficient to abolish most of the late, use-dependent inactivation of NavAb. In addition to modulating the extent of use-dependent inactivation, the progressively truncated constructs showed decremental slowing of the decay of sodium current during depolarizations. NaVAb-α40 has voltage-independent kinetics of current decay, while other constructs have differential profiles of decay kinetics that are correlated with C-terminal length. Our experiments reveal a surprisingly crucial role for the C-terminal domain, which forms a coiled-coil structure unique to bacterial sodium channels, in both early and late phases of use-dependent slow inactivation of NaVAb.