d) Valine Note: its side chain doesn\'t contain acidic H such as those in NH or COOH group. Thus, pH value doesn\'t affect the charge since no protonation or deprotonation happens. Solution d) Valine Note: its side chain doesn\'t contain acidic H such as those in NH or COOH group. Thus, pH value doesn\'t affect the charge since no protonation or deprotonation happens..