We demonstrate for the first time the formation of a fluid lipid bilayer membrane on mesoporous silicon substrates for bioapplications. Using fluorescence recovery after photobleaching, the diffusion ...coefficients for the bilayers supported on oxidized, amino-, and biotin-functionalized mesoporous silicon were determined. The biodetection of a single human umbilical vein endothelial cell was accomplished using confocal microscopy and exploiting Foerster resonance energy transfer effects after the incorporation of RGD covalently linked lipid soluble dyes, with fluorescence donor and acceptor components, within the fluid membrane. A signal response of greater than 100% was achieved via the clustering of RGD peptides binding with areas of high integrin density on the surface of a single cell. These results are a testament to the usefulness of such functional molecular assemblies, based on mobile receptors, mimicking the cell membrane in the development of a new generation of biosensors.
An electrochemical method to determine alanine aminotransferase (ALT) activity over its normal and elevated physiological range was developed based upon detection of
l-glutamate at a glutamate ...oxidase-modified platinum electrode. Measurements were carried out in the presence of ALT co-substrates
l-alanine and α-ketoglutarate and current response from either the oxidation of hydrogen peroxide or the re-oxidation of the mediator ferrocene carboxylic acid was employed. The enzyme electrode was tested over a 6-month period and found to retain 79% of its original activity towards ALT detection with >200 measurements performed over this time. Signals associated with interfering electroactive species (ascorbic acid and uric acid) were eliminated using background subtraction at a denatured glutamate oxidase enzyme electrode. The sensitivity of the device was found to be 0.845
nA
U
−1
L ALT with
t
90
=
180
s, linear range 10–1000
U
L
−1 and LOD of 3.29
U
L
−1 using amperometry at
E
app
=
0.4
V vs. Ag/AgCl at 308
K (35
°C).
Hepatitis C virus (HCV) cannot be grown in vitro, making biochemical identification of new drug targets especially important. HCV p7 is a small hydrophobic protein of unknown function, yet necessary ...for particle infectivity in related viruses Harada, T. et al., (2000) J. Virol. 74, 9498–9506. We show that p7 can be cross-linked in vivo as hexamers. Escherichia coli expressed p7 fusion proteins also form hexamers in vitro. These and HIS-tagged p7 function as calcium ion channels in black lipid membranes. This activity is abrogated by Amantadine, a compound that inhibits ion channels of influenza Hay, A.J. et al. (1985) EMBO J. 4, 3021–3024; Duff, K.C. and Ashley, R.H. (1992) Virology 190, 485–489 and has recently been shown to be active in combination with current HCV therapies.
The discipline of molecular electronics has grown rapidly over the last 10 years and is driven by the promise of the enhanced applied physical properties of functionalised organic materials compared ...to their inorganic partners. The subject can be divided generally into two broad themes, namely active molecular-scale electronics (or photonics), in which the control or generation of charge (or photons) at the nanoscale is attempted, and passive supra-molecular electronics (or photonics), in which the specific functionality of the molecules is modified by some interaction or process. In this paper, an example of the latter approach to molecular electronics will be given and this will describe the gas sensing properties of a tetra-substituted porphyrin molecule. The optical absorbance spectrum of LB film assemblies of 5,10,15,20-tetrakis(3,4-bis2-ethylhexyloxyphenyl)-21H,23H-porphine (EHO) is highly sensitive to low concentrations of NO
2. LB films prepared at much faster than conventional deposition rates (∼1000 mm min
−1) yield
t
50 response and recovery times of 25 and 33 s, respectively, and show a sensitivity of 60% relative absorbance change (at 430 nm) for 4.4 ppm NO
2. The morphology of these films is revealed using atomic force microscopy to contain isolated micron-size domains which are composed of grains of several nm in diameter. This unconventional structure leads to a useful sensing material as a result of the molecular functionality of the porphyrin coupled to the enhanced surface area of the porous film assembly. The EHO film shows a gradually diminishing optical response as its temperature is increased, resulting from the shift in the adsorption–desorption equilibrium towards desorption. The spectrum recovers fully after exposure to NO
2. The rate of recovery is slow at room temperature but can be accelerated dramatically with gentle heating (∼350 K) for a few seconds. The kinetics of the gas sensing process have been modelled and found to fit Elovichian surface adsorption for an initial fast surface adsorption process. This is followed by a much slower diffusive process in which the NO
2 molecules diffuse through the bulk of the assembly. The concentration dependence of the optical response over the range 0.8–4.4 ppm follows a Langmuir model.
New ferrocene derivatives, (6-(4-(1H-pyrrol-1-yl)phenoxy)hexyl) ferrocene (1) and ((4-(1H-pyrrol-1-yl)phenoxy)carbonyl) ferrocene (2) were synthesized, characterized, and electrochemically evaluated ...as redox active films formed via anodic oxidation with pyrrole. Thin film studies were conducted and films formed from both compounds resulted in a stable Fe
II/III
redox couple with E
o
= 0.035 V and 0.365 V vs. Ag/Ag
+
for (1) and (2), respectively. Both potential sweeping and chronocolometry were employed for film formation with the former resulting in controllable, reproducible film deposition. Growth conditions and solution concentrations were varied in order to assess influence on electrochemical behavior. Surface coverage was of the order 10
−8
-10
−9
mol cm
−2
, surface confined behavior (i
p
vs. ν) was evident up to 0.2 V s
−1
with semi-infinite diffusion (i
p
vs. ν
1/2
) dominating at higher scan rates. Laviron theory was employed where possible for the determination of electron transfer co-efficient and rate constants.
Colloidal lithography on mica has been combined with subsequent thermal evaporation, sputtering, and template‐stripping processes to produce ultraflat ternary nanopatterns of large lateral extension ...(see Figure). The resulting surface is particularly useful for applications that demand proper distinction between complex surface chemistry and topography.
Summary
1. Current national and international frameworks for assessing threats to species have not been developed in the context of climate change, and are not framed in a way that recognises new ...opportunities that arise from climate change.
2. The framework presented here separates the threats and benefits of climate change for individual species. Threat is assessed by the level of climate‐related decline within a species’ recently occupied (e.g. pre‐1970s) historical distribution, based on observed (e.g. repeat census) and/or projected changes (e.g. modelled bioclimate space). Benefits are assessed in terms of observed and/or projected increases outside the recently occupied historical range.
3. Exacerbating factors (e.g. small population size, low dispersal capacity) that might increase levels of threat or limit expansion in response to climate change are taken into consideration within the framework. Protocols are also used to identify levels of confidence (and hence research and/or monitoring needs) in each species’ assessment.
4. Observed and projected changes are combined into single measures of expected decline and increase, together with associated measures of confidence. We weight risk classifications towards information that is most certain. Each species is then placed in one of six categories (high risk, medium risk, limited impact, equivalent risks & benefits, medium benefit, high benefit) reflecting whether climate change is expected (or has been observed) to cause net declines or increases in the region considered, based on the balance of benefits and threats.
5. We illustrate the feasibility of using the framework by applying it to (i) all British butterflies (N = 58 species) and (ii) an additional sample of British species: 18 species of plants, bats, birds and beetles.
6. Synthesis. Our framework assesses net declines and increases associated with climate change, for individual species. It could be applied at any scale (regional, continental or global distributions of species), and complements existing conservation assessment protocols such as red‐listing. Using observed and projected population and/or range data, it is feasible to carry out systematic conservation status assessments that inform the development of monitoring, adaptation measures and conservation management planning for species that are responding to climate change.
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