There has been a large number of reports on the thermal behaviour of/3-1actoglobul:in solutions, as measured calorimetrically, mostly either at or about neutral pH [1-6] or under very acid condition.,; where the protein exists as a
monomer [7-12]. At acid pH, measurements have been made over two orders of magnitude in concentration, down
to a few mg/ml and have ~hown little effect of concentration on the position of the maximum in the thermogram
(Tmax). However, all of tile reported investigations near neutral pH were made at concentrations considerably
greater than the naturally occurring level of fl-lactoglobulin in cow's milk of about 3.1 mg/ml [13]. These studies also showed that there was only a small dependence of the temperature of the maximum in the thermogram (Tma x) on the protein concentration, C, [6]. It was nevertheless of interest to know whether calorimetric measurements
at neutral pH, previously made at concentrations in excess of 50 mg/ml, for reasons of instrumental sensitivity, reflect the behaviour of the protein at the typical concentrations of milk. To cover the widest possible range
of concentrations and temperature scanning rates (o~), two different calorimeters were employed, namely a Perkin-
Elmer DSC7 for the higher concentrations and scanning rates and a more sensitive Microcal MC-2 calorimeter, able to record thermograms of reasonable quality down to concentrations comparable to that of fl-lactoglobulin in cow's milk. Both instruments are of the power compensation type.
There has been a large number of reports on the thermal behaviour of/3-1actoglobul:in solutions, as measured calorimetrically, mostly either at or about neutral pH [1-6] or under very acid condition.,; where the protein exists as amonomer [7-12]. At acid pH, measurements have been made over two orders of magnitude in concentration, downto a few mg/ml and have ~hown little effect of concentration on the position of the maximum in the thermogram(Tmax). However, all of tile reported investigations near neutral pH were made at concentrations considerablygreater than the naturally occurring level of fl-lactoglobulin in cow's milk of about 3.1 mg/ml [13]. These studies also showed that there was only a small dependence of the temperature of the maximum in the thermogram (Tma x) on the protein concentration, C, [6]. It was nevertheless of interest to know whether calorimetric measurementsat neutral pH, previously made at concentrations in excess of 50 mg/ml, for reasons of instrumental sensitivity, reflect the behaviour of the protein at the typical concentrations of milk. To cover the widest possible rangeof concentrations and temperature scanning rates (o~), two different calorimeters were employed, namely a Perkin-Elmer DSC7 for the higher concentrations and scanning rates and a more sensitive Microcal MC-2 calorimeter, able to record thermograms of reasonable quality down to concentrations comparable to that of fl-lactoglobulin in cow's milk. Both instruments are of the power compensation type.
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