Solution to the isotope dilution challenge

Abstract

The award entitles the winning groups to select a Springer book of their choice up to a value of €100,-.Our Congratulations! SolutionOver the years, isotope dilution mass spectrometry (IDMS) has witnessed many reformulations. One of the earliest expressions for this quantitation model was given by the single isotope dilution (ID 1 MS). In ID 1 MS, the mass fraction of an analyte A is obtained from mass spectrometric analysis of a mixture (blend) of sample and an isotopically-enriched form of the analyte (B) which acts as an internal standard:This model requires that the mass fraction of the isotopic standard (w B ), the isotopic composition of natural (R A ) and enriched (R B ) material, and their respective molar masses (M A and M B ) are known beforehand. It is possible, however, to design an experiment in order to bypass the prior knowledge of these quantities. For example, in addition to the blend of sample and isotopic standard (AB), one can prepare and measure three additional blends of a primary standard (with natural isotopic composition) and isotopic standard. These blends are denoted A*B-1, A*B-2, A*B-3, and the following system of four equations now describes the experiment, assuming R A =R A* and M A =M A* :Equation 2 can be solved for w A to yield:whereThis article is the solution to the Analytical Challenge to be found at http://dx

Nanobody Based Immunoassay for Human Soluble Epoxide Hydrolase Detection Using Polymeric Horseradish Peroxidase (PolyHRP) for Signal Enhancement: The Rediscovery of PolyHRP?

“…Anti-human sEH VHHs and rabbit polyclonal antibody were prepared as described in our previous work 29,31 . Streptavidin-HRP conjugate (SA-HRP) was purchased from SouthernBiotech (Birmingham, Al).…”

“…This graph is plotted based on the data from work of ref 29; (b) format C: PolyHRP based format using biotinylated nanobody (A1 or A9, 1 μg/mL) as the detection antibody and SA-PolyHRP (25 or 50 ng/mL) as the tracer; (c) expanded low concentration range of Figure 2b. Error bars indicate standard deviations ( n = 3).…”

“… a Results are average ± SD (CV, n=3); 1 nM sEH corresponds to 62.5 ng/mL sEH. b,c,d Data from ref 40, 29, 30, respectively. …”

“…This work has been hampered by the lack of quantitative tests other than the semi-quantitative Western blots. Our group recently screened ten clones generating haemagglutinin (HA)-tagged nanobodies against human sEH from a llama VHH phage display library and developed a polyclonal/nanobody sandwich immunoassay for human sEH detection using a nanobody as the detection antibody 29 . Its format is shown in Figure 1a and this ELISA (format A) is termed conventional ELISA throughout the paper.…”

The Application of Whole Cell-Based Biosensors for Use in Environmental Analysis and in Medical Diagnostics

“…Here, multiple biosensors were prepared using a combination of regulatory proteins such as CadC, ZntR, and ArsR, which then simultaneously responded when several different metals were added [ 75 , 76 ]. In another example, for the purpose of improving the specific and accurate detection of bioavailable Cd, Pb and As in a co-contaminated environment, a tailored whole cell biosensor set ( Figure 5 ) was prepared by analyzing a E. coli sensor set using binary regression and binary linear equations to minimize the interference in signal generated when different metals (such as Cd, Pb and As) were presented [ 77 ].…”