The invention provides improved methods to prepare protein conjugates from a ketone-modified protein. In one embodiment, the protein is prepared by linking two free cysteines by reaction with a 1,3-dihaloacetone or similar ketone-containing reactant, linking the sulfur atoms of the two cysteines together. The ketone inserted between the sulfur atoms is then used to form an oxime, thus conjugating the protein to a payload. In another embodiment, two cysteine residues are tied together by reaction with a 1,3-dihaloacetone or similar reactant, and the new ketone is used to form an oxime with a suitable payload molecule, thus conjugating the protein to a payload. The method provides improved reaction conditions for the oxime formation, whereby higher yields and improved product homogeneity are achieved.本發明提供用以自酮修飾蛋白質製備蛋白質共軛物的經改良之方法。在一個實施例中，該蛋白質係藉由以下製備：藉由與1,3-二鹵丙酮或類似含酮反應物反應來鍵聯兩種游離半胱胺酸，將該兩種半胱胺酸之硫原子鍵聯在一起。隨後使用插入該等硫原子之間的酮來形成肟，因此共軛該蛋白質至有效負載物。在另一實施例中，兩種半胱胺酸殘基藉由與1,3-二鹵丙酮或類似反應物反應而連接在一起，且使用新的酮來形成具有合適有效負載分子的肟，因此共軛該蛋白質至有效負載物。該方法為肟形成提供經改良之反應條件，由此達成較高產率及經改良之產物均質性。
