A method for increasing the relaxivity of a contrast agent having a metal ion complexed to a chelator is disclosed. The metal ion complex is tethered to the remainder of the molecule by at least two points of attachment such that local motion is limited and higher relaxivity can be achieved. In one non-limiting example version of the invention, the alanine analogue of Gd(DOTA), Gd(DOTAIa) wherein Gd is gadolinium and DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid was integrated into polypeptide structures. This resulted in very rigid attachment of the metal ion complex to the peptide backbone. Rigid molecular structures provide fewer degrees of rotational freedom, resulting in greater control over the rotational dynamics and resultant relaxivity. In the case of Gd(DOTAIa), the metal complex is tethered to the peptide via the amino acid side chain to the DOTA moiety and via a dative bond from an amide oxygen to the Gd(lll) ion.
揭示了一种增加对比剂弛豫率的方法,该对比剂具有与
螯合剂络合的
金属离子。
金属离子络合物通过至少两个连接点与分子的其余部分相连,从而限制局部运动并实现更高的弛豫率。在发明的一个非限制性示例版本中,将Gd(DO
TA)的丙
氨酸类似物Gd(DO
TAIa)(其中Gd为
钆,DO
TA为1,4,7,10-四
氮杂环十二酸-1,4,7,10-
四乙酸)整合到
多肽结构中。这导致
金属离子复合物与肽骨架的非常刚性连接。刚性分子结构提供较少的旋转自由度,从而更好地控制旋转动力学和结果弛豫率。在Gd(DO
TAIa)的情况下,
金属络合物通过
氨基酸侧链与DO
TA基团相连,并通过
酰胺氧原子与Gd(lll)离子之间的配位键相连。