CHRISTIAN DE DUVE 



the two pigments. Their carbon-monoxide compounds were found 

 particularly suitable for this purpose. The Beckmann spectrophoto- 

 meter was used for the determinations. 



Standard absorption curves were carefully determined for solutions 

 of pure CO-haemoglobin and CO-myoglobin, the latter being purified 

 and crystallized according to a method previously reported 1 . The 

 pigments were dissolved in M/15 Na 2 HP0 4 and pure CO was bubbled 

 through the solution after addition of an excess of Na 2 S 2 4 . The 

 solution was then poured into a 1 cm cuvette, care being taken to fill 

 the cuvette completely and to cover it immediately. Readings were 

 taken at a number of wave-lengths on pure solutions and on mixtures. 

 The applicability of Beer's law was checked by varying the dilution 

 widely. 



to 



0-75 



0-50 



0-25 



Figure 1. Standard extinction 

 curves of CO-Hb (•—•), 

 CO-Mgb (O— O) and light- 

 filter (x — x) 



£ = extinction coefficient for 



C = 1 gm/l of dry pigment 



and d = 1 cm 



600 580 560 S40 



Wavelength >n mp. 



520 



Figure 1 shows part of the spectral curves of pure CO-Hb and 

 CO-Mgb in the range of the alpha and beta bands. For differential 

 measurements it was found very convenient to take readings at 575-7 mp 

 (isobestic point) and at 568 and 583-8 my., where CO-Mgb has identical, 

 CO-Hb widely different extinction-coefficients. The following simple 

 set of equations is then valid : 



126 



