Marks D L, Buchsbaum R, Swain T
Anal Biochem. 1985 May 15;147(1):136-43. doi: 10.1016/0003-2697(85)90019-3.
A method for measuring total protein in situ in plant samples has been developed using the determination of amino acids released by acid hydrolysis of dried plant material. Standard proteins and plant samples were hydrolyzed with 3% sulfuric acid at 100 degrees C for 24 h and the amino acids released were measured with ninhydrin. Unhydrolyzed plant extracts were also analyzed for free amino acids with ninhydrin. Total amino acid equivalents (protein plus free amino acids) of a diverse set of plant samples was significantly correlated with total protein as estimated by elemental analysis (N X 6.25). The Lowry method as modified by precipitation of proteins with trichloroacetic acid was found to be unsatisfactory for dried plant samples due to the incomplete extractability of proteins. Although some alkaloids caused increased absorbance with ninhydrin, interference with quantification of protein is likely to be minimal. Tannins interfered with the Lowry and Bradford methods but not the ninhydrin method.
一种利用测定干燥植物材料经酸水解释放的氨基酸来原位测量植物样品中总蛋白的方法已被开发出来。标准蛋白和植物样品在100℃下用3%硫酸水解24小时，并用茚三酮测定释放的氨基酸。未水解的植物提取物也用茚三酮分析游离氨基酸。一系列不同植物样品的总氨基酸当量（蛋白质加游离氨基酸）与元素分析（氮×6.25）估算的总蛋白显著相关。用三氯乙酸沉淀蛋白质改进的洛氏法对于干燥植物样品来说并不令人满意，因为蛋白质的提取不完全。尽管一些生物碱会导致茚三酮吸光度增加，但对蛋白质定量的干扰可能很小。单宁酸干扰了洛氏法和考马斯亮蓝法，但不干扰茚三酮法。
