Proteins can evolve by accumulating changes on amino acid sequences. These changes are mainly caused by missense mutations on its DNA coding sequences. Mutations with neutral or positive effects on fitness can be maintained while deleterious mutations tend to be eliminated by natural selection. Amino acid changes are influenced by the biophysical, chemical, and biological properties of amino acids. There is a multiplicity of amino acid properties that can influence the function and expression of proteins. Amino acid properties can be expressed into numerical indexes, which can help to predict functional and structural aspects of proteins and allow statistical inferences of selection pressure on amino acid usage. The accuracy of these analyses may be compromised by the existence of several numerical indexes that measure the same amino acid property, and the lack of objective parameters to determine the most accurate and biologically relevant index. In the present study, the gradient consistency test was used in order to estimate the magnitude of directional selection imparted by amino acid biochemical and biophysical properties on protein evolution.

蛋白质可以通过积累氨基酸序列的变化来进化。这些变化主要是由其 DNA 编码序列的错义突变引起的。可以保持对适应度具有中性或积极影响的突变，而自然选择往往会消除有害突变。氨基酸的变化受氨基酸的生物物理、化学和生物学特性的影响。有多种氨基酸特性可以影响蛋白质的功能和表达。氨基酸特性可以表示为数字索引，这有助于预测蛋白质的功能和结构方面，并允许对氨基酸使用的选择压力进行统计推断。这些分析的准确性可能会因存在多个测量相同氨基酸特性的数值指标而受到影响，并且缺乏客观参数来确定最准确和生物学相关的指标。在本研究中，使用梯度一致性检验来估计氨基酸生化和生物物理特性对蛋白质进化的定向选择的大小。