Matt Prior continued his superb start to the county season with an invaluable century to prevent a Sussex collapse, but Nottinghamshire dominated day one.
The wicket-keeper came to the crease at 33-4, before Sussex slumped to 75-6.
However, Prior marched on to 131 from 174 balls, dominating a seventh-wicket stand of 142 in 26 overs with Robin Martin-Jenkins, to help Sussex to 277.
Sussex's bowlers then got the ball swinging to reduce the hosts to 46-2 by stumps, Adam Voges unbeaten on 19.
Jason Lewry removed Notts opener Matt Wood with one that swung into the batsman's pads, before Martin-Jenkins bowled Will Jefferson off an inside-edge.
The fall of 12 wickets on the first day only served to highlight the class of Prior's knock, who passed 500 first-class runs for the season having failed to make a half-century only once so far.
Darren Pattinson was again at the forefront of Notts' fine bowling efforts, yorking Chris Nash and having Michael Yardy caught behind, before Charlie Shreck had Carl Hopkinson caught at mid-on.
Chris Adams was then caught at slip off Pattinson to bring up Sussex's second duck and when Murray Goodwin cut Paul Franks to point and Luke Wright poked Shreck to cover, the county champions were in dire straits.
However, Prior enjoyed a practically faultless display, starting slowly before racing past 100, taking only 42 balls to go from 50 to his century.
It was left to spinner Graeme Swann to wrap up the Sussex innings, having Martin-Jenkins caught off a mis-sweep before bowling Prior round his legs off an inside-edge and finally removing Lewry to finish with impressive figures of 3-52 off 14.3 overs.
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