Interaction of HMG proteins and H1 with hybrid PNA–DNA junctions

The objective of this study was to evaluate the effects of inserting peptide nucleic acid (PNA) sequences into the protein‐binding surface of an immobilized four‐way junction (4WJ). Here we compare the classic immobile DNA junction, J1, with two PNA containing hybrid junctions (4WJ‐PNA₁ and 4WJ‐PNA₃). The protein interactions of each 4WJ were evaluated using recombinant high mobility group proteins from rat (HMGB1b and HMGB1b/R26A) and human histone H1. In vitro studies show that both HMG and H1 proteins display high binding affinity toward 4WJ's. A 4WJ can access different conformations depending on ionic environment, most simply interpreted by a two‐state equilibrium between: (i) an open‐x state favored by absence of Mg²⁺, low salt, and protein binding, and (ii) a compact stacked‐x state favored by Mg²⁺. 4WJ‐PNA₃, like J1, shifts readily from an open to stacked conformation in the presence of Mg⁺², while 4WJ‐PNA₁ does not. Circular dichroism spectra indicate that HMGB1b recognizes each of the hybrid junctions. H1, however, displays a strong preference for J1 relative to the hybrids. More extensive binding analysis revealed that HMGB1b binds J1 and 4WJ‐PNA₃ with nearly identical affinity (K_Ds) and 4WJ‐PNA₁ with two‐fold lower affinity. Thus both the sequence/location of the PNA sequence and the protein determine the structural and protein recognition properties of 4WJs.     

Using community-owned resource persons to provide early diagnosis and treatment and estimate malaria burden at community level in north-eastern Tanzania

ABSTRACT: BACKGROUND: Although early diagnosis and prompt treatment is an important strategy for control of malaria, using fever to initiate presumptive treatment with expensive artemisinin combination therapy is a major challenge; particularly in areas with declining burden of malaria. This study was conducted using community-owned resource persons (CORPs) to provide early diagnosis and treatment of malaria, and collect data for estimation of malaria burden in four villages of Korogwe district, north-eastern Tanzania. METHODS: In 2006, individuals with history of fever within 24 hours or fever (axillary temperature [greater than or equal to]37.5degreesC) at presentation were presumptively treated using sulphadoxine/pyrimethamine. Between 2007 and 2010, individuals aged five years and above, with positive rapid diagnostic tests (RDTs) were treated with artemether/lumefantrine (AL) while under-fives were treated irrespective of RDT results. Reduction in anti-malarial consumption was determined by comparing the number of cases that would have been presumptively treated and those that were actually treated based on RDTs results. Trends of malaria incidence and slide positivity rates were compared between lowlands and highlands. RESULTS: Of 15,729 cases attended, slide positivity rate was 20.4% and declined by >72.0% from 2008, reaching <10.0% from 2009 onwards; and the slide positivity rates were similar in lowlands and highlands from 2009 onwards. Cases with fever at presentation declined slightly, but remained at >40.0% in under-fives and >20.0% among individuals aged five years and above. With use of RDTs, cases treated with AL decreased from <58.0% in 2007 to <11.0% in 2010 and the numbers of adult courses saved were 3,284 and 1,591 in lowlands and highlands respectively. Malaria incidence declined consistently from 2008 onwards; and the highest incidence of malaria shifted from children aged <10 years to individuals aged 10-19 years from 2009. CONCLUSIONS: With basic training, supervision and RDTs, CORPs successfully provided early diagnosis and treatment and reduced consumption of anti-malarials. Progressively declining malaria incidence and slide positivity rates suggest that all fever cases should be tested with RDTs before treatment. Data collected by CORPs was used to plan phase 1b MSP3 malaria vaccine trial and will be used for monitoring and evaluation of different health interventions. The current situation indicates that there is a remarkable changing pattern of malaria and these areas might be moving from control to pre-elimination levels.     

Highly selective single nucleotide polymorphism recognition by a chiral (5S) PNA beacon

A chiral peptide nucleic acid (PNA) beacon containing a C-5 modified monomer based on L-lysine was synthesized. The terminal amino group of the lysine side chain was linked to a spacer for future applications on surfaces. The PNA beacon bears a carboxyfluorescein fluorophore and a dabcyl quencher at opposite ends. The DNA binding properties were compared with those of a homologous PNA beacon containing only achiral monomers. Both beacons underwent a fluorescence increase in the presence of complementary DNA, with higher efficiency and higher selectivity (evaluated using single mismatched DNA sequences) observed for the chiral monomer containing PNA. Ion exchange (IE) HPLC with fluorimetric detection was used in combination with the beacon for the selective detection of complementary DNA. A fluorescent peak corresponding to the PNA beacon:DNA duplex was observed at a very low detection limit (1 nM). The discriminating capacity of the chiral PNA beacon for a single mismatch was found to be superior to those observed with the unmodified one, thus confirming the potency of chirality for increasing the affinity and specificity of DNA recognition.     

Antidote effect of sodium fluoride against organophosphate poisoning in mice

Pretreatment of mice with atropine (17.4 mg/kg) + NaF (5 or 15 mg/kg) had a significant antidotal effect over atropine alone against the lethality produced by soman and sarin. Atropine + NaF (15 mg/kg) was effective against tabun, whereas the lower dose of NaF was not. An effect of NaF on organophosphate inhibited acetylcholinesterase could not account for the antidotal action of NaF. NaF had no effect on liver somanase activity but inhibited aliesterase activity. Aliesterase activity in NaF pretreated somanpoisoned mice was significantly (p < 0.05) higher than in those receiving atropine alone. In CBDP-pretreated mice NaF did not significantly attenuate the toxicity of soman. It is hypothesized that the antidotal effect of NaF versus organophosphate poisoning is due to its antidesensitizing action at nicotinic receptors in the neuromuscular junction and/or sympathetic ganglia in addition to the proposed increased hydrolysis of sarin and direct detoxification of tabun.     

ACETYLCHOLINESTERASE TURNOVER IN BRAIN, CEREBROSPINAL FLUID AND PLASMA

—By assay of acetylcholine hydrolysis to measure total cholinesterase activity and acetyl-β-methylcholine hydrolysis to measure acetylcholinesterase (E.C 3.1.1.7) activity, patterns of regeneration of enzyme activity were measured in seven areas of brain, cerebrospinal fluid and plasma of cats after administration of an irreversible inhibitor. Halftimes of recovery of total cholinesterase in the brain tissues ranged from 0·9 to 3·8 days (av = 2·5 days) and acetylcholinesterase recovery halftimes ranged from 1·2 to 5·3 days (av = 3·6 days). Regeneration of total cholinesterase was also followed in subcellular fractions of guinea-pig and rat brains after similar inhibition. In both species, the fastest recovery occurred in the soluble fraction with halftimes of 1·8 and 1·6 days, while the synaptosomal fractions exhibited the slowest recoveries with halftimes of 8·3 and 4·1 days. Regeneration of activity in plasma and CSF most nearly resembled that of the soluble brain fraction.     

Short-Range Surface Plasmon Polaritons for Extraordinary Low Transmission Through Ultra-Thin Metal Films with Nanopatterns

We provide both experimental and theoretical investigation on extraordinary low transmission through one-dimensional nanoslit and two-dimensional nanohole arrays on ultra-thin metal films. Unambiguous proofs demonstrate that short-range surface plasmon polaritons play a key role leading to this novel phenomenon, which could be useful for creating new polarization filters and other integrated plasmonic components.