Table 1.

Comparison of procedures for concentration of turkey coronavirus (TCoV)

Procedures	Total volume (ml)	Total proteina (mg)	Total HA activity (unit)	Specific activityb (unit/mg)	Recoveryc (%)
(1) 3000×g supd	20	156	64 000	410	100
30% cushion ppte	4	12	1600	133	2.5
(2) 3000×g sup	25	195	80 000	410	100
60% cushion bandf	4	63	53 760	853	67.2
(3) 3000×g sup	10	78	6400	82	100
(NH4)2SO4 pptg	2.3	25	1472	60	23.0

^aProtein concentration was determined by the method of Lowry et al. (1951).

^bSpecific activity=total HA activity/total protein.

^cRecovery=total HA activity of d or e/total HA activity of d.

^dSupernatants from centrifugation of infected turkey embryo intestinal homogenates at 3000×g for 10 min.

^ePrecipitates from ultracentrifugation of 3000×g sup at 100 000×g through a 15 ml cushion of 30% (w/v) sucrose solution for 1 h.

^fOpalescent band from ultracentrifugation of 3000×g sup at 100 000×g through a 5 ml cushion of 60% (w/v) sucrose solution for 1 h.

^gPrecipitates from treatment of 3000×g sup with 50% saturated ammonium sulfate and low speed centrifugation (8000×g).