Guanidine hydrochloride (Aminoformamidine Hydrochloride) is a strong organic base existing primarily as guanidium ions at physiological pH. It is found in the urine as a normal product of protein metabolism. It is also used in laboratory research as a protein denaturant.

Guanidine HCl 是一种蛋白质变性剂。[1] 低浓度Guanidine HCl 能够重塑酸性展开的肌红蛋白和细胞色素c，稳定熔融球状态。[2] Guanidine HCl 展开核糖核酸酶的效果是尿素的2.8倍，但对溶菌酶仅是1.7倍。不同蛋白质在特定pH值下Guanidine HCl 的△GWaterapp.值分别为：核糖核酸酶 9.7 Cal/mole（pH 6.6）、溶菌酶 6.1（pH 2.9）、α-胰蛋白酶 8.3 （pH 4.3）、以及β-乳球蛋白11.7（pH 3.2）。[3] Guanidine HCl 能够有效消除酵母细胞中的[PSI+]元素。5 mM Guanidine HCl 的生长培养基能抑制酵母的[PSI+]及其它朊病毒的[PSI+]。[4] Guanidine HCl 降低了Hsp104恢复热变性荧光素酶活性的能力。[5]