Overview of Label-Free Quantification Service in Creative Proteomics

Creative Proteomics, as one of leader suppliers in drug development services, provides label-free quantification methods, which are aiming at the relative quantification and absolute quantification. And this service is welcome by majority of customers, who are working on protein quantification and other related fields.

Theory: Label-free quantification depends on precursors’ signal strength or chromatography count. The former is applicable for high-precision mass spectrometry. HRMS level makes label-free quantification process become possible. Label-free quantification aims to determine the relative amount of proteins in two or more biological samples. Compared with other methods for protein quantification, label-free quantification method has made a great difference in Creative Proteomcis.

There are two types of label-free quantification methods: one is based on the parent ion intensity of the first spectrum; the other is based on the number of matched secondary spectrum of peptide.

Methods for label-free quantification in Creative Proteomics

Signal strength method: In traditional proteomics process, protease firstly should be cut into peptides and separated by liquid Chromatography. Separating and eluting peptides according to its different hydrophobicity, ionic strength and isoelectric points. And then using electrospray ionization source to generate gas phase ion. Mass spectrometer record and isolate in the light of their mass charge ratio, which is called parent ion scanning. Under the condition of secondary fragmentation, ion spectra of secondary fragmentation can be obtained. And then returning to parent ion scan for the next cycle, which is commonly known as data dependent acquisition model. In the first mass spectrum, each parent ions includes three-dimensional information---HPLC retention time, ionic strength and mass charge ratio. Science the precursor ion signal intensity got by electrospray ionization is correlated with the ion concentration and each parent ion is ionized peptides, ion peak intensity extracted from first mass spectrum to identify peptides is able to reflect the abundance of peptides. Commonly used parameters of ion peak intensity are peaks height, peak area and peak volume, etc..

Spectrum counting: Generally speaking, higher the protein abundance, more peptides generated by digestion; the more tryptic peptides, the more unique match peptides analyzed and identified by mass spectrometry. Of course, the number of the corresponding secondary spectrum will also be more. This is the basis of label-free quantification in view of spectrum counts. So it is also being believed as a simple approach to protein relative quantification. Spectral counts model reflects protein abundance by adding up the number of secondary spectra of all peptides.

Technical feature

This service in Creative Proteomics has following featured characteristics

Free labeling:

it can be utilized in large scale sample without any limitation.

High data requirements:

accurate results are obtained based on high experimental repeatability.

Quantitative methods:

different protein quantification can be achieved based on information analysis

Large amount of data: high requirement of information analysis

These two approaches are the basic ones for label-free quantification and also utilized widely in protein quantification fields. Considering the benefit of most our customers, Creative Proteomics also has the promotion activities until 19th this month, hoping all customers can find their own needs during this period with great discount. What’s more, you can enjoy up to 20% discount.