week 2_2 Flashcards
what is a biomarker/molecular biomarker?
characteristic that is objectively measured and evaluated -> biological molecule that provides valuable information
one type of biomarker relevant for epilepsy, fraction?
volatile biomarker -> breath metabolomics
VERY small fraction of the breath (0.1%)
principle of mass spectrometry, main components
generate ions from inorganic or organic compounds and separate them by mass to charge ratio -> qualitative and quantitative detection
sample inlet, ion source, mass analyzer, detector
explain briefly electrospray ionization
Voltage applied to capillary tube -> electric field causes liquid at tip to form a spray of positively charged droplets -> solvent evaporates as droplets travel -> when they become small enough = coulomb fission -> forms gas phase ions
how does time of flight work?
m/z = 2eUt^2/s^2
s is the drift path
time of flight correlates to molecular weight
what is the isotopic mass? how do you calculate it?
exact mass of an isotope (not the same as nominal mass)
u = 1/12 of mass of one atome of 12C -> 1 u = 1.66x10^-27 kg
absolute mass accuracy, and relative mass accuracy
absolute = difference between measured m/z and calculated m/z
relative (in ppm) = absolute mass accuracy / (m/z)
-> less than 1 ppm is very good
formula for mass resolution
R = m/delta_m = (m/z) / delta(m/z)
smallest difference that can be separated for a given signal
what is the workflow for breath analysis?
kid breathes in machine -> analysis of exhaled metabolites -> MS fingerprint
in parallel : blood sample -> drug level measurements -> find concentration of analyte
try to correlate MS and blood results -> can we predict blood concentration with MS peaks?
what are other potential uses of breath analysis for epileptic patients?
- check how the drug is metabolized at an individual level
- prediction of total and free drug
