primary 

可以定量出所有N-端氨基和赖氨酸支链
氨基。而且毋需HPLC或水解什么的。

Trinitrobenzene sulfonic acid(TNBS) assay for amino groups

  sensitivity:5-100 nmolesof primary amino groups
Reference: Fields, R.(1972) Meth. Enzymol.25:464-468(reduce
volumes by 50%)

  Solutions:
   0.1M Na2SO3 (stable for 1 week)
   0.1M NaH2PO4
   0.1M Na2B4O7/0.1M NaOH
   1.1M TNBS in water
  standard: 1mM glycine

   Reagent A: 0.1M Na2B4O7/0.1M NaOH
   Reagent B:1.5 parts 0.1M Na2SO3, 98.5 parts 0.1M NaH2PO4

  Protocol:
1. pipet sample into 12x75 mm glass tubes, bring volume up to a final
volume of 250 ul with water. Use 5-100 nmoles of glycine as standard
2. add 250 ul of Reagent A to each sample. Vortex
3. Add 10ul of 1.1M TNBS reagent reagent to each sample. Vortex. Sit
at room temperature for 10 minutes.
4. Add 1ml of Reagent B to each sample. Vortex.
5. Read absorbance at 420nm. Zero detector against water blank sample