Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, 11 Carol I, 700506 Iasi, Romania.
Environmental Science Laboratory (LSE), Nangui-Abrogoua University, Abidjan 02 BP 801, Côte d'Ivoire.
Molecules. 2024 Sep 12;29(18):4341. doi: 10.3390/molecules29184341.
Tryptophan is an essential amino acid deficient in cereals, especially maize. However, maize ( L.) is the main source of protein in some developing countries in Africa and Latin America. In general, the nutritional profile of cereals is poor, because they are deficient in essential amino acids such as tryptophan and lysine due to a relatively higher proportion of alcohol-soluble proteins. Quality protein maize (QPM) has been developed through genetic manipulation for the nutritional enrichment of maize to address these problems. Nevertheless, methods for protein, lysine and tryptophan are time-consuming and require relatively large amounts of samples. Therefore, we have advanced here a simple, cheap, fast, reliable and robust procedure for the determination of protein and tryptophan in the same biuret supernatant, which can also be used for chemical characterization of other cereals. Samples of 50 mg maize ground to pass through a 0.1 mm screen were sonicated for 5 min. in eppendorf vials with 1.5 mL of a biuret reagent each. After centrifugation and protein determination by biuret, 0.2 mL of supernatant was treated with 0.8 mL of a tryptophan reagent. Both total protein and tryptophan can be determined in microplates at 560 nm to speed up the measurements. The main advantage of the new micro-method is the rapid estimation of the nutrient quality of maize samples by a single weighing of a small amount of valuable plant materials.
色氨酸是谷物中（尤其是玉米）缺乏的必需氨基酸。然而，玉米是非洲和拉丁美洲一些发展中国家的主要蛋白质来源。总的来说，谷物的营养状况不佳，因为它们缺乏必需氨基酸，如色氨酸和赖氨酸，这是由于醇溶性蛋白质的比例相对较高。通过遗传操作开发了优质蛋白玉米（QPM），以解决这些问题，使玉米的营养得到丰富。然而，用于蛋白质、赖氨酸和色氨酸的方法耗时且需要相对大量的样品。因此，我们在这里提出了一种简单、廉价、快速、可靠和强大的方法，用于在同一样品的双缩脲上清液中同时测定蛋白质和色氨酸，该方法也可用于其他谷物的化学特性分析。将 50 毫克通过 0.1 毫米筛的玉米样品在 1.5 毫升双缩脲试剂的 eppendorf 管中超声处理 5 分钟。离心后，用双缩脲法测定蛋白质，取 0.2 毫升上清液，用 0.8 毫升色氨酸试剂处理。总蛋白和色氨酸均可在微孔板中于 560nm 处测定，以加快测量速度。新的微量方法的主要优点是通过对少量有价值的植物材料进行单次称重，快速估计玉米样品的营养质量。
