Diffraction patterns from small protein crystals illuminated by highly coherent X-rays often contain measurable interference signals between Bragg peaks. This coherent `shape transform' signal introduces enough additional information to allow the molecular densities to be determined from the diffracted intensities directly, without prior information or resolution restrictions. However, the various correlations amongst molecular occupancies/vacancies at the crystal surface result in a subtle yet critical problem in shape transform phasing whereby the sublattices of symmetry-related molecules exhibit a form of partial coherence amongst lattice sites when an average is taken over many crystal patterns. Here an iterative phase retrieval algorithm is developed which is capable of treating this problem; it is demonstrated on simulated data.

中文翻译：

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锋利纳米晶体的形状变换定相

高度相干 X 射线照射的小蛋白质晶体的衍射图案通常在布拉格峰之间包含可测量的干扰信号。这种相干的“形状变换”信号引入了足够的附加信息，允许直接根据衍射强度确定分子密度，而无需先验信息或分辨率限制。然而，晶体表面分子占据/空位之间的各种相关性导致形状变换定相中的一个微妙但关键的问题，即当对许多晶体取平均值时，对称相关分子的亚晶格在晶格位点之间表现出部分相干的形式模式。这里开发了一种迭代相位检索算法，能够解决这个问题；它在模拟数据上得到了证明。