Experiments performed with biological systems require a buffer that will not interfere with the stability and activities of the biological components. In 1966, Norman Good and his colleagues began a series of investigations that established criteria for new zwitterionic buffers that would be optimal for experimentation with biological systems. These criteria included: a. pKa between 6 and 8
b. highly water soluble
c. minimally permeable to biological membranes
d. minimal effects of salt concentration
e. minimal effect of temperature on pKa (pKa/°C)
f. minimal effect of concentration on pKa minimal interaction with metal ions non-toxic
g. high chemical stabilit
h. minimal absorbance between 240-700 nm
For each buffer, choose the property that does not meet Good's criteria for biochemical buffers If all of the buffer's properties satisfy the criteria for a Good's buffer:
Properties of acetate buffer: Properties of MOPS buffer:
1. highly water soluble pKa at 25°C 7.15
2. ApKJ°C=-0.0002 ΔpKJ°C =-0.013
3. pKg at 25°C = 4.76 absorbs light at <230 nm
4. does not cross lipid bilayer does not cross lipid bilayer
5. all the above properties fulfill all the above properties fulfil
the lipid criteria the lipid criteria