Amino acids which have an asymmetric carbon can exist in two forms: D (dextro-rotary or right-handed) and L (levo-rotary or left-handed). L forms can transform to D forms and back, randomly (racemizing). Living organisms make and use L forms. Dead protein has a mixture. The longer it has been dead, the closer the D/L ratio may come to 1/1.
2010 Arthur V. Chadwick, Ph.D.