Protein quantitation analysis, label-free

As the name suggests, label-free quantification does not require the incorporation of an isotopic label into peptides for quantitation of relative concentrations. Each sample is separately prepared, subjected to individual LC/MS runs, and quantification is performed through analysis of their mass spectra. There are two approaches used for label-free quantification. The first approach is based on the assumption that peptide/protein levels follow a linear relationship with area under the curve of the ion spectra. This method involves quantitation of relative levels by comparing the peak intensity of ions from multiple peptides. But experimental variations in sample preparation and... 

Sohd supported membranes immobihzed on quartz resonators allow for the detection and quantification of protein-membrane and membrane-membrane interactions mediated by proteins. The advantage of the QCM technique is not only that a label-free monitoring of proteins is possible, but also that the good time resolution allows for a detailed quantitative analysis of kinetics, as demonstrated in this chapter by means of Monte Carlo simulations. Moreover, since the quartz oscillation is not only sensitive to... 

Label-free methods use the intrinsic properties of proteins to report binding events on protein chips. Ciphergen ProteinChips can be incorporated directly into a matrix-assisted laser desorbtion/ionization (MALDI) source of a mass spectrometer, which can identify the proteins and provide quantitative analysis. The ionization of proteins bound to Protein-Chips is enhanced by the properties of the chip surface, leading to more uniform mass spectra than possible with standard MALDI mass spectrometric... 

DNA oxidation at carbon electrodes is associated with the irreversible oxidation of guanine and adenine [33], For example, the G oxidation signal observed at -i-1.0 V, without external labels, has been used to monitor telomerase activity by using a carbon graphite electrode (CGE) as an electrochemical transducer [5], Telomerase activity has been detected in cell extracts containing as low as 100 ng pl of protein. This label-free assay is practical in the quantitative determination of telomerase activity providing a cheap and simple detection protocol for the diagnosis of cancer that can also be extended to the analysis of food related to DNA. 

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