Table 1.

O₂ affinities (P₅₀, mmHg) and Hill’s cooperativity coefficients (n₅₀) for high- and low-altitude deer mouse Hbs measured at 37° and 25°C in 0.1 M Hepes buffer at varying pH values (heme 0.3 mM) and in the absence (stripped) and presence of KCl and DPG, as indicated. P₅₀ and n₅₀ values are derived from nonlinear regression of the sigmoidal Hill equation to 4–6 saturation points measured for each condition and are expressed as means±SEM. The corresponding overall enthalpy of oxygenation (kJ mol O₂⁻¹) calculated at pH 7.20 is indicated.

	High						Low
temperature	37 °C			25 °C		ΔH	37 °C			25 °C		ΔH
pH	7.41	6.92	6.53	7.26	6.56	7.20	7.41	6.91	6.55	7.27	6.57	7.20
P50 (mmHg)
stripped	9.17±0.41	17.3±0.5	32.6±2.2	6.32±0.27	14.4±0.7	−11.0	9.2±0.22	17.8±0.5	28.5±1.1	6.20±0.20	14.9±0.4	−11.4
+KCl	13.5±0.5	23.5±0.9	37.3±3.2	8.40±0.33	16.6±1.0	−12.3	16.7±0.5	25.1±0.6	40.1±0.9	9.84±0.32	20.1±0.6	−12.3
+DPG	12.0±0.4	26.8±0.6	43.8±2.6	10.4±0.6	19.0±0.8	−7.9	13.6±0.4	29.3±1.3	48.0±1.5	10.5±0.3	23.2±0.6	−9.6
+KCl+DPG	15.1±0.5	27.5±0.7	44.7±1.8	10.7±0.4	24.7±1.3	−10.1	16.3±0.3	30.5±0.5	52.3±1.8	11.7±0.4	28.1±1.0	−9.6
Hill coeff. (n50)
stripped	1.94±0.14	1.75±0.07	1.79±0.18	1.63±0.11	1.46±0.10		2.03±0.09	1.86±0.09	1.76±0.09	1.61±0.08	1.02±0.01
+KCl	2.02±0.13	2.04±0.13	1.92±0.26	1.87±0.13	1.96±0.21		2.03±0.11	2.04±0.09	2.43±0.12	2.06±0.12	1.87±0.10
+DPG	2.00±0.13	2.48±0.12	2.11±0.22	1.81±0.20	1.95±0.15		2.20±0.14	2.30±0.22	2.51±0.17	2.11±0.15	2.26±0.13
+KCl+DPG	2.11±0.11	2.32±0.13	2.33±0.19	2.05±0.15	1.72±0.13		2.27±0.08	2.53±0.10	2.40±1.76	2.08±0.14	2.00±0.13