MAGNETIC FIELD & APPLICATION FOR MR SUSCEPTIBILITY QUANTIFICATION

我们正在开发一系列用于监测基因的策略 心理治疗。第一种方法是监测特定的表型。 遗传病。例如，在粘多糖病III型中 (MPS VII)遗传缺陷是不能产生-葡萄糖醛酸酶。我们 正在合成含氟酚的葡萄糖醛酸类化合物。当 糖苷键被19F化学位移-葡萄糖苷酸酶切割 释放出的苯酚的含量预计将变化约10ppm； 此外，由于释放的碎片是阴离子的，因此预期 被困在牢房里。囊性纤维化的基因缺陷是 在氯离子运输车(CFTR)中。已知这会导致 空气通道中钠和氯化物浓度的增加 体液。因此，我们正在开发多种量子23Na方法 以检测和量化这种钠浓度的变化。在……里面 高胆固醇血症遗传缺陷是缺乏低密度脂蛋白受体。 我们正在开发用磁铁矿标记低密度脂蛋白分子的方法 MRI可检测到低密度脂蛋白向肝脏溶酶体的转运。 这些例子展示了磁共振方法是如何 开发用于监测酶、离子传输和基因缺陷的遗传缺陷 感受器。然而，我们认识到，发展各种方法来 监测遗传缺陷的表型将需要大量的资金 也不会完全可靠，因为相似的基因类型 可表达为不同的表型或可表达为 程度不同。一种更通用的方法是开发一个合适的 标记基因，可以连接到转染体上，并且 由同一发起人表达的。MRI检测的理想标记物 可能是磁铁矿，它增加了水的弛豫度，这是 110M的质子。磁铁矿的含量也高出约1000倍。 松弛程度高于等量的铁(例如如果在 铁蛋白的铁核)。某些细菌具有独特的能力 从铁中提炼磁铁矿。造成这种现象的蛋白质是什么？ 已经在细菌和哺乳动物中克隆并表达了活性 细胞。我们正在探索这种蛋白质作为一种标记的用途 基因疗法。

We are developing a number of strategies for monitoring gene therapy. The first approach is to monitor the specific phenotype of the genetic disease. For example, in mucopolysaccharidosis type VII (MPS VII) the genetic defect is failure to produce -glucuronidase. We are synthesizing glucuronides of fluorinated phenols. When the glycosidic bond is cleaved by -glucuronidase , the 19F chemical shift of the liberated phenol is expected to change by about 10ppm; furthermore, since the liberated fragment is anionic, it is expected to be trapped in the cell. In cystic fibrosis the genetic defect is in the chloride transporter (CFTR). This is known to result in an increase in the sodium and chloride concentrations in air passage fluids. We, therefore, are developing multiple quantum 23Na methods to detect and quantitate this alteration in sodium concentration. In hypercholesteremia the genetic defect is the lack of LDL receptors. We are developing methods to label LDL mole cules with magnetite so that delivery of LDL to liver lysosomes could be detected by MRI. These examples demonstrate how magnetic resonance methods can be developed to monitor genetic defects in enzymes, ion transport and receptors. However, we recognize that development of methods to monitor phenotypes of genetic defects will required an immense amount of effort and will not be completely reliable since similar genotypes may be expressed as different phenotypes or may be expressed to different extents. A more general approach is to develop a suitable marker gene that could be attached to the transfection vector and expressed by the same promotor. An ideal marker for MRI detection would be magnetite, which increases the relaxivity of water, which is 110 M in protons. Magnetite also has about a thousandfold higher relaxivity than an equivalent amount of iron (such as if found in the iron core of ferritin). Certain bacteria have the unique ability to produce magnetite from iron. T he protein responsible for this activity has been cloned and expressed in both bacterial and mammalian cells. We are exploring the utility of this protein as a marker for gene therapy.