Effects of Cations and PH on Antimicrobial Activity of Thanatin and s-Thanatin against _Escherichia coli_ ATCC25922 and _B. subtilis_ ATCC 21332

Thanatin and s-thanatin were insect antimicrobial peptides which have shown potent antimicrobial activities on a variety of microbes. In order to investigate the effect of cations and pH on the activity of these peptides against Gram-negative bacteria and Gram-positive bacteria, the antimicrobial activities of both peptides were studied in increasing concentrations of monovalent cations (K^+^ and Na^+^), divalent cations (Ca^2+^ and Mg^2+^) and H^+^. The NCCLS broth microdilution method showed that both peptides were sensitive to the presence of cations. The divalent cations showed more antagonized effect on the activity against Gram-negative bacteria than the monovalent cations, since the two peptides lost the ability to inhibit bacterial growth at a very low concentration. In addition, the activities of both peptides tested were not significantly affected by pH. Comparing to studies of other antibacterial peptide activities, our data support a hypothesis that positive ions affect the sensitivity to cation peptides

Polyelectrolyte Condensation Induced by Linear Cations

We examine the role of the condensing agent in the formation of polyelectrolyte bundles, via grand-canonical Monte Carlo simulations. Following recent experiments we use linear, rigid divalent cations of various lengths to induce condensation. Our results clarify and explain the experimental results for short cations. For longer cations we observe novel condensation behavior owing to alignment of the cations. We also study the role of the polyelectrolyte surface charge density, and find a nonmonotonic variation in bundle stability. This nonmonotonicity captures two trends that have been observed in separate experiments.Comment: To appear in Physical Review Letter

Mössbauer characterisations and magnetic properties of iron cobaltites CoxFe3−xO4 (1 ≤ x ≤ 2.46) before and after spinodal decomposition

Iron cobaltite powders CoxFe3_xO4 (1 ≤ x ≤ 2.46) were synthesized with compositions in between the cobalt errite CoFe2 O4 and Co2.46Fe0.54O4. The cationic distribution of pure spinel phases was determined by Mossbauer spectroscopy: as Co content increases in the spinel oxide, Co3+ cations replace Fe3+ cations in the octahedral sites and Co2+ cations migrate from octahedral to tetrahedral sites. Saturation magnetizations MS measured at 5 K by a SQUID magnetometer were consistent with the values calculated from the cationic distribution. MS decreases as diamagnetic Co3+ cations replace strongly magnetic Fe3+ cations. Two spinel phases were formed by spinodal decomposition of Co1.73Fe1.27O4 phase submitted to a subsequent thermal treatment, one with a high amount of iron Co1.16Fe1.84O4 and one other containing mostly cobalt Co2.69Fe0.31O4. Increase of the experimental MS value obtained after the spinodal decomposition is in accordance with the calculated value deduced from the cationic distribution of the two phases

Mechanistic insights into allosteric regulation of the A2A adenosine G protein-coupled receptor by physiological cations.

Cations play key roles in regulating G-protein-coupled receptors (GPCRs), although their mechanisms are poorly understood. Here, 19F NMR is used to delineate the effects of cations on functional states of the adenosine A2A GPCR. While Na+ reinforces an inactive ensemble and a partial-agonist stabilized state, Ca2+ and Mg2+ shift the equilibrium toward active states. Positive allosteric effects of divalent cations are more pronounced with agonist and a G-protein-derived peptide. In cell membranes, divalent cations enhance both the affinity and fraction of the high affinity agonist-bound state. Molecular dynamics simulations suggest high concentrations of divalent cations bridge specific extracellular acidic residues, bringing TM5 and TM6 together at the extracellular surface and allosterically driving open the G-protein-binding cleft as shown by rigidity-transmission allostery theory. An understanding of cation allostery should enable the design of allosteric agents and enhance our understanding of GPCR regulation in the cellular milieu

Non-genetic risk and protective factors for sporadic degenerative and vascular young onset dementia

Young onset dementia (with symptom onset before age 65, YOD) has a significant personal and public health impact. Despite this, little is known about its cause and non-genetic factors have been sparsely investigated. Existing studies have not considered the timing or severity of exposure, which is important in late onset dementia (LOD). They have also failed to exclude directly-inherited cases and those occurring secondarily to another disease. This thesis examined the risk for sporadic degenerative and vascular YOD associated with six selected non-genetic factors: cognitive reserve enhancing factors, cardiovascular risk factors, smoking, depression, alcohol use, and traumatic brain injury (TBI). It established the role of exposure timing and severity, as well as interrelationships existing between factors. Data were taken from two epidemiological studies conducted in Sydney, Australia, one of which exclusively included Aboriginal and Torres Strait Islander participants. Dementia diagnosis was confirmed via clinical consensus and risk exposure was retrospectively self- and/or informant-reported. Participants were 96 people with YOD (58.4% with Alzheimer’s disease) and 179 age-group and sex matched control participants. Poor educational attainment, low lifetime participation in cognitive leisure activity, stroke or TIA, smoking, and heavy alcohol use were significantly related to risk for primary degenerative and vascular YOD. Some compensation for low educational attainment was possible via a complex occupation later in life. The effect of hypertension and depression varied depending on when they occurred relative to dementia onset. There was no effect of mild-moderate alcohol use, hypercholesterolemia, diabetes, or TBI of any kind. Cumulative risk exposure was detrimental, particularly where lack of access to or participation in cognitive-reserve enhancing factors clustered with cardiovascular risk factors. The results of this thesis suggest that non-genetic factors have a role in YOD as they do in LOD. Compared with their same-age peers, people with YOD experience a lifetime of disadvantage starting from early in life. The timing and severity of exposure, as well as the potential for compensation with later protective exposures, are important considerations. Efforts to address early life disadvantage and facilitate upward social mobility will be beneficial in delaying dementia to later in life

Group 13 Decamethylmetallocenium Cations

Salts containing the decamethylmetallocenium cations, [( C5Me5) M-2](+) ( or Cp*M-2(+)) of the group 13 "metals" B, Al and Ga have been prepared using a variety of synthetic routes. Precursor molecules of the type Cp*2MX ( X = Cl, Br, Me) exhibit structural features that vary significantly depending on the size and electronegativity of the central atom. While salt metathesis, halide abstraction and methanide abstraction methods represent viable routes for the preparation of salts of Cp*B-2(+) and Cp*Al-2(+), acidolysis of a Cp* group from Cp*Ga-3 is the most reliable method for the synthesis of the analogous gallium cation. Gallocenium cations are less stable than either of the lighter congeneric cations since they prove to be susceptible to decomposition reactions involving the "back-transfer" of ligands from the counter anion. Density functional theory (DFT) calculations revealed that, whereas Cp*Ga-2(+) is predicted to adopt a molecular structure more similar to that of Cp*B-2(+), the electronic structure of the gallium cation bears a greater resemblance to that of Cp*Al-2(+).Chemistr

Neuropsychiatric symptoms of dementia in those with and without a recorded history of psychological trauma: A comparative study from an Australian dementia support service

Objective: To compare the number and severity of neuropsychiatric symptoms (NPS) and associated caregiver distress between those with and without a noted history of psychological trauma among those referred to a specialised national dementia NPS support service. Methods: This was a 5-year retrospective observational study of records from the Dementia Support Australia NPS support service. NPS were reported by formal or informal caregivers at service entry using the Neuropsychiatric Inventory Nursing Home version or Questionnaire version. A history of psychological trauma was recorded in the person\u27s social or medical history and/or endorsed as a contributor to NPS by a trained dementia consultant after a comprehensive clinical review. Regression was used to examine the impact of a recorded history of psychological trauma on NPS severity and associated caregiver distress, controlling for age and sex. Results: Among 41,876 eligible referrals with dementia, 6% (n = 2529) had some reference in their records to a history of psychological trauma. Referrals with a recorded history of psychological trauma were rated with a higher rate of both NPS severity (mean = 12.0) and associated caregiver distress (mean = 16.5) at service entry than those without a recorded history of psychological trauma (means = 10.7 and 14.5, respectively). A recorded history of psychological trauma was associated with higher odds of psychotic symptoms, agitation/aggression, irritability, disinhibition, affective symptoms and night-time behaviours. Conclusions: Traumatic stress symptoms may represent a neglected target for intervention to reduce the impact of NPS in people with dementia