Data from: A nuclear magnetic resonance study of water in aggrecan solutions

Aggrecan, a highly charged macromolecule found in articular cartilage, was investigated in aqueous salt solutions with proton nuclear magnetic resonance. The longitudinal and transverse relaxation rates were determined at two different field strengths, 9.4 T and 0.5 T, for a range of temperatures and aggrecan concentrations. The diffusion coefficients of the water molecules were also measured as a function of temperature and aggrecan concentration, using a pulsed field gradient technique at 9.4 T. Assuming an Arrhenius relationship, the activation energies for the various relaxation processes and the translational motion of the water molecules were determined from temperature dependencies as a function of aggrecan concentration in the range 0–5.3% w/w. The longitudinal relaxation rate and inverse diffusion coefficient were approximately equally dependent on concentration and only increased by upto 20% from that of the salt solution. The transverse relaxation rate at high field demonstrated greatest concentration dependence, changing by an order of magnitude across the concentration range examined. We attribute this primarily to chemical exchange. Activation energies appeared to be approximately independent of aggrecan concentration, except for that of the low-field transverse relaxation rate, which decreased with concentration.

聚集蛋白聚糖（Aggrecan）是存在于关节软骨中的高带电大分子，本研究采用质子核磁共振（proton nuclear magnetic resonance）技术对其在盐水水溶液中的相关特性展开探究。研究分别在9.4 T与0.5 T两种磁场强度下，测定了一系列温度与聚集蛋白聚糖浓度条件下的纵向弛豫速率与横向弛豫速率；同时采用脉冲场梯度技术（pulsed field gradient technique），在9.4 T磁场下测定了水分子扩散系数随温度与聚集蛋白聚糖浓度的变化关系。基于阿伦尼乌斯（Arrhenius）关系，结合0–5.3%质量分数（w/w）范围内聚集蛋白聚糖浓度对弛豫过程与水分子平动运动的温度依赖性，我们推导得到了各对应过程的活化能。结果显示，纵向弛豫速率与扩散系数的倒数均呈现近似一致的浓度依赖性，相较于纯盐水溶液，其数值最大增幅仅为20%；高场下的横向弛豫速率展现出最强的浓度依赖性，在本次考察的浓度区间内变化幅度可达一个数量级。我们将该现象主要归因于化学交换（chemical exchange）。除低场横向弛豫速率对应的活化能随浓度升高而降低外，其余所有过程的活化能均近似与聚集蛋白聚糖浓度无关。