Koenig S H, Brown R D, Ugolini R
IBM T. J. Watson Research Center, Yorktown Heights, NY 10598.
Magn Reson Med. 1993 Jan;29(1):77-83. doi: 10.1002/mrm.1910290114.
Protein in water solution increases magnetic relaxation rates of solvent nuclei to an extent that depends on magnetic field strength and molecular weight. Koenig and Schillinger (J. Biol. Chem. 244, 3283 (1969)) showed that a small fraction of the water molecules in the first hydration shell, bound irrotationally with a residence lifetime in the range 0.1 to 10 microseconds, would account for the phenomena. No experiments, as yet, have proven the existence of such long-lived waters, nor yielded a value for their lifetime. Analogous measurements on solutions of both denatured and cross-linked protein give data different from that of native protein, but much like results for tissue. By comparing proton and deuteron relaxation rates in solutions of native and cross-linked protein, it is possible to demonstrate the existence of these relatively long-lived waters; the data indicate that 1% of a monolayer of the waters of hydration of protein have lifetimes that cluster near 1 microsecond and, it is argued, are held in place by multiple hydrogen bonds. Assigning shorter lifetimes for waters held by fewer bonds, it is possible to develop a unified view of relaxation of water nuclei in protein solutions and in tissue, and to relate it to recent crystallographic data on hydrated protein.
水溶液中的蛋白质会使溶剂原子核的磁弛豫速率增加，增加的程度取决于磁场强度和分子量。凯尼格和席林格（《生物化学杂志》244, 3283 (1969)）表明，第一层水化层中的一小部分水分子，以非旋转方式结合，停留寿命在0.1到10微秒范围内，可解释这一现象。目前尚无实验证明这种长寿命水的存在，也未得出其寿命值。对变性和交联蛋白质溶液进行的类似测量得到的数据与天然蛋白质不同，但与组织的结果非常相似。通过比较天然和交联蛋白质溶液中的质子和氘核弛豫速率，可以证明这些相对长寿命水的存在；数据表明，蛋白质水化水单层的1%具有聚集在1微秒左右的寿命，据认为，这些水是由多个氢键固定在位的。为通过较少键结合的水赋予较短的寿命，可以对蛋白质溶液和组织中水分子的弛豫形成统一的观点，并将其与最近关于水化蛋白质的晶体学数据联系起来。
