Protein determination by nuclear magnetic resonance

Abstract

Protein may be determined using a pulsed nuclear magnetic reso‐nance (NMR) spectrometer in conjunction with a relaxation reagent. These reagents exhibit characteristic nuclear relaxation rates, controlled by a paramagnetic ingredient such as copper, and these rates are altered if substances are added which can bind the copper. The method is fast and simple. Sample and reagent are mixed, brought to a standard temperature and transferred to the spectrom‐eter for measurement. Sample throughput can be high since the time for the spectrometer reading is on the order of 30 sec. Compositions and methods of use are given for 2 copper‐based reagents together with the results on a number of materials. The alkaline copper reagent gives a very similar response to different types of protein and it appears suitable for meat, fish and for other protein materials low in carbohydrates. It shows a response to carbohydrate which depends strongly on type. The acid copper reagent is intended for measurements of vegetable or seed protein and similar applications where carbohydrate is present. This reagent does not respond to carbohydrates tested; the response to protein depends on the type of protein.