The use of carbon and gold electrodes in anodic stripping voltammetric heavy metal sensors.

The use of anodic stripping voltammetry (ASV)has been proven in the past to be a precise and sensitive analytical method with an excellent limit of detection. Electrochemical sensors could help to avoid expensive and time consuming procedures as sample taking and storage and provide a both sensitive and reliable method for the direct monitoring of heavy metals in the aquatic environment. Solid electrodes which have been used in this work, were produced using previously developed methods. Commercially available and newly designed, screen printed carbon and gold plated working electrodes (WE) were compared. Good results were achieved with the screen printed and plated electrodes under conditions optimized for each electrode material. The electrode stability, reproducibility of single measurements and the limit of detection obtained for Pb were satisfactory (3*10-6mol/l on screen printed carbon WEs after 60 s of deposition and 6*10-6 mol/l on gold plated WEs after 5 min of deposition). Complete 3-electrode-sets (counter, reference and working electrode) were screen printed on different substrates (glass, polycarbonate and alumina). Also here, both carbon and gold were used as WE. Using 3-electrode-sets with a gold plated WE on glass was a limit of detection of 7*10-7 mol/l was achieved after only 60 s of deposition.

One-Electron Reduction of 2-Nitrotoluene, Nitrocyclopentane, and 1-Nitrobutane in Room Temperature Ionic Liquids: A Comparative Study of Butler–Volmer and Symmetric Marcus–Hush Theories Using Microdisk Electrodes

The voltammetry for the reduction of 2-nitrotoluene at a gold microdisk electrode is reported in two ionic liquids: trihexyltetradecylphosphonium tris(pentafluoroethyl)trifluorophosphate ([P-14,P-6,P-6,P-6][FAP]) and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([Emim][NTf2]). The reduction of nitrocyclopentane (NCP) and 1-nitrobutane (BuN) was investigated using voltammetry at a gold microdisk electrode in the ionic liquid [P-14,P-6,P-6,P-6][FAP]. Simulated voltammograms, generated through the use of ButlerVolmer theory and symmetric MarcusHush theory, were compared to experimental data, with both theories parametrizing the data similarly well. An experimental value for the Marcusian parameter, 1 was also determined in all cases. For the reduction of 2-nitrotoluene, this was 0.5 +/- 0.1 eV in both solvents, while for NCP and BuN in [P-14,P-6,P-6,P-6][FAP], it was 2 +/- 0.1 and 5 +/- 0.1 eV, respectively. This is attributed to the localization of charge on the nitro group and the primary nitro alkyls increased interaction with the environment, resulting in a larger reorganization energy.

Monitoring of saliva pH using miniaturized sensing tools as an indicator of oral health

The monitoring of oral disease is important, not alone for oral health, but for the detection and prevention of
systemic disease. The link between oral health and systemic disease is the focus of many studies, with
indications emerging of a causal link [1]. For disease diagnostics, blood has typically been the fluid of choice
for analysis, the retrieval of which is invasive and therefore unsuitable for wearable technology. Analysis of
saliva, however, is less invasive than that of blood, requires little or no pre-treatment and is abundantly
available. A strong correlation has been found between the analytes of blood and saliva [2] with saliva
containing biomarkers for diseases such as diabetes, oral cancer and cardiovascular disease. The development of
an implantable multi-parametric wireless sensor, to monitor both salivary analytes and changes in gingival
temperature, is the aim of this research project.
The aim of our current study is to detect changes in salivary pH, using a gold electrode with a pHsensitive
iridium oxide layer, and an Ion Sensitive Field Effect Transistor probe. Characterisation studies were
carried out in artificial saliva (AS). A salivary pH of between 4.5pH-7.5pH [3], and gingival temperature
between 35°C-38°C [4], were identified as the target range of interest for the human oral environment. Sensor
measurements were recorded in solutions of varying pH and temperature. An ISFET probe was then implanted
into a prototype denture and characterised in AS. This study demonstrates the suitability of ISFET and gold
electrode pH sensors for incorporation into implantable oral sensors.
[1] G. Taylor and W. Borgnakke, “Periodontal disease: associations with diabetes, glycemic control and
complications,” Oral Dis., vol. 14, no. 3, pp. 191–203, Apr. 2008.
[2] E. Tékus, M. Kaj, E. Szabó, N. L. Szénási, I. Kerepesi, M. Figler, R. Gábriel, and M. Wilhelm,
“Comparison of blood and saliva lactate level after maximum intensity exercise,” Acta Biol. Hung., vol. 63
Suppl 1, pp. 89–98, 2012.
[3] S. Naveen, M. L. Asha, G. Shubha, A. Bajoria, and A. Jose, “Salivary Flow Rate, pH and Buffering
Capacity in Pregnant and Non Pregnant Women - A Comparative Study,” JMED Res., pp. 1–8, Feb. 2014.
[4] A. F. Holthuis and F. S. Chebib, “Observations on temperature and temperature patterns of the gingiva. I.
The effect of arch, region and health,” J. Periodontol., vol. 54, no. 10, pp. 624–628, Oct. 1983

PH-sauvagine from the skin secretion of Phyllomedusa hypochondrialis: a novel CRF-like peptide with smooth muscle contraction activity

Amphibian skin, and particularly that of south/Central American phyllomedusine frogs, is supposed to be "a huge factory and store house of a variety of active peptides". The 40 amino acid amphibian CRF-like peptide, sauvagine, is a prototype member of a unique family of these Phyllomedusa skin peptides. In this study, we describe for the first time the structure of a mature novel peptide from the skin secretion of the South American orange-legged leaf frog, Phyllomedusa hypochondrialis, which belongs to the amphibian CRF/sauvagine family. Partial amino acid sequence from the N-terminal was obtained by automated Edman degradation with the following structure: pGlu-GPPISIDLNMELLRNMIEI-. The biosynthetic precursor of this novel sauvagine peptide, consisted of 85 amino acid residues and was deduced from cDNA library constructed from the same skin secretion. Compared with the standard sauvagine from the frog, Phyllomedusa sauvagei, this novel peptide was found to exert similar contraction effects on isolated guinea-pig colon and rat urinary bladder smooth muscle preparations.

Direct Visual Indication of pH Windows: 'Off-On-Off' Fluorescent PET (Photoinduced Electron Transfer) Sensors/Switches

1–3, which contain a fluorophore and two proton receptors with opposite PET (photoinduced electron transfer) characteristics, only display strong fluorescence within a pH window whose position and width are tunable.

Arenedicarboximide Building Blocks for Fluorescent Photoinduced Electron Transfer pH Sensors Applicable with Different Media and Communication Wavelengths

N-(aminoalkyl)-4-chloronaphthalene-
1,8-dicarboximides 1, N-
(aminoalkyl)-4-acetamidonaphthalene-
1,8-dicarboximides 3 and N,N'-bis(aminoalkyl)-
perylene-3,4:9,10-tetracarboxydiimides
4 show good fluorescent off ±
on switching in aqueous alcoholic solution
with protons as required for fluorescent
PET sensor design. The excitation
wavelengths lie in the ultraviolet
(lmaxˆ345 and 351 nm) for 1 and 3 and
in the blue-green (lmaxˆ528, 492 and
461 nm) for 4; the emission wavelengths
lie in the violet (lmaxˆ408 nm) for 1, in
the blue (lmaxˆ474 nm) for 3 and in the
yellow-orange (lmaxˆ543 and 583 nm)
for 4. Compound 4b shows substantial
fluorescence enhancement with protons
when immobilized in a poly(vinylchloride)
matrix, provided that 2-nitrophenyloctyl
ether plasticizer and potassium
tetrakis(4-chlorophenyl)borate additive
are present to prevent dye crystallization
and to facilitate proton diffusion
into the membrane, respectively.

High-affinity NO3 --H+ cotransport in the fungus Neurospora:Induction and control by pH and membrane voltate

High-affinity nitrate transport was examined in intact hyphae of Neurospora crassa using electrophysiological recordings to characterize the response of the plasma membrane to NO₃ ^- challenge and to quantify transport activity. The NO₃ ^--associated membrane current was determined using a three electrode voltage clamp to bring membrane voltage under experimental control and to compensate for current dissipation along the longitudinal cell axis. Nitrate transport was evident in hyphae transferred to NO₃ ^--free, N-limited medium for 15 hr, and in hyphae grown in the absence of a nitrogen source after a single 2-min exposure to 100 μM NO₃ ^-. In the latter, induction showed a latency of 40-80 min and rose in scalar fashion with full transport activity mensurable approx. 100 min after first exposure to NO₃ ^-; it was marked by the appearance of a pronounced sensitivity of membrane voltage to extracellular NO₃ ^- additions which, after induction, resulted in reversible membrane depolarizations of (+)54-85 mV in the presence of 50 μM NO₃ ^-; and it was suppressed when NH₄ ⁺, was present during the first, inductive exposure to NO₃ ^-. Voltage clamp measurements carried out immediately before and following NO₃ ^- additions showed that the NO₃ ^--evoked depolarizations were the consequence of an inward-directed current that appeared in parallel with the depolarizations across the entire range of accessible voltages -400 to +100 mV). Measurements of NO₃ ^- uptake using NO₃ ^--selective macroelectrodes indicated a charge stoichiometry for NO₃ ^- transport of 1(+):1(NO₃ ^-) with common K(m) and J(max) values around 25 μM and 75 pmol NO₃ ^- cm^-2sec^-1, respectively, and combined measurements of pH(o) and [NO₃ ^-](o) showed a net uptake of approx. 1 H⁺ with each NO₃ ^- anion. Analysis of the NO₃ ^- current demonstrated a pronounced voltage sensitivity within the normal physiological range between -300 and -100 mV as well as interactions between the kinetic parameters of membrane voltage, pH(o) and [NO₃ ^-](o). Increasing the bathing pH from 5.5 to 8.0 reduced the current and the associated membrane depolarizations 2- to 4-fold. At a constant pH(o) of 6.1, driving the membrane voltage from -350 to -150 mV resulted in an approx. 3-fold reduction in the maximum current and a 5-fold rise in the apparent affinity for NO₃ ^-. By contrast, the same depolarization effected an approx. 20% fall in the K(m) for transport as a function in [H⁺](o). These, and additional results are consistent with a charge-coupling stoichiometry of 2(H⁺) per NO anion transported across the membrane, and implicate a carrier cycle in which NO binding is kinetically adjacent to the rate-limiting step of membrane charge transit. The data concur with previous studies demonstrating a pronounced voltage-dependence to high-affinity NO₃ ^- transport system in Arabidopsis, and underline the importance of voltage as a kinetic factor controlling NO₃ ^- transport; finally, they distinguish metabolite repression of NO₃ ^- transport induction from its sensitivity to metabolic blockade and competition with the uptake of other substrates that draw on membrane voltage as a kinetic substrate.

The effect of soil pH on rhizosphere carbon flow of Lolium perenne

Perennial rye-grass plants were grown at 15°C in microcosms containing soil sampled from field plots that had been maintained at constant pH for the last 30 years. Six soil pH values were tested in the experiment, with pH ranging from 4.3-6.5. After 3 weeks growth in the microcosms, plant shoots were exposed to a pulse of ¹⁴C-CO₂. The fate of this label was determined by monitoring ¹⁴C-CO₂ respired by the plant roots/soil and by the shoots. The ¹⁴C remaining in plant roots and shoots was determined when the plants were harvested 7 days after receiving the pulse label. The amount of ¹⁴C (expressed as a percentage of the total ¹⁴C fixed by the plant) lost from the plant roots increased from 12.3 to 30.6% with increasing soil pH from 4.3 to 6. Although a greater percentage of the fixed ¹⁴C was respired by the root/soil as soil pH increased, plant biomass was greater with increasing soil pH. Possible reasons for observed changes in the pattern of ¹⁴C distribution are discussed and, it is suggested that changes in the soil microbial biomass and in plant nitrogen nutrition may, in particular be key factors which led to increased loss of carbon from plant roots with increasing soil pH. © 1990 Kluwer Academic Publishers.

FLAG-idarubicin and allogeneic stem cell transplantation for Ph-positive ALL beyond first remission

We describe a single centre experience of eight consecutive patients with relapsed or refractory Ph+ ALL treated with the FLAG/idarubicin regimen followed by BMT or PBSCT. Following FLAG/idarubicin, one achieved a partial response and seven CR. All patients subsequently received allogeneic transplants: one sibling BMT, three matched unrelated (MUD) BMT and four sibling PBSCT. Two patients received second transplants with PBSC from their original BM donors following FLA/Ida with no further conditioning. Three patients are alive in CR 9, 24 and 32 months after transplant. Seven of eight patients had a cytogenetic response following FLAG/Ida induction and one of seven became bcr-abl negative. All eight patients had a complete cytogenetic response following transplant. Four of five assessable patients became p190 bcr-abl negative after transplant; three of these subsequently relapsed. Both patients with the p210 bcr-abl transcript remained bcr-abl positive in CR after transplant. FLAG/Ida was well tolerated and appears to be effective in inducing remission in relapsed Ph+ ALL. The use of FDR-containing chemotherapy without further conditioning prior to PBSCT deserves further study in heavily pre-treated patients and, in patients with relapsed ALL following BMT, may be a safer option than DLI (donor lymphocyte infusion) by avoiding the associated risk of aplasia.