6533b7ddfe1ef96bd1273c89

RESEARCH PRODUCT

Adsorption Structures of Amino Acids on Calcite(104)

subject

description

Elucidating the interaction details of proteins with the most stable cleavage plane of calcite , namely calcite(104), is of great importance for understanding the physicochemical mechanisms behind biomineralisation. In this context, amino acids are generally believed to serve as suitable model molecules, as they constitute the basic building blocks of proteins. In this work, we present a non-contact atomic force microscopy (NC-AFM) investigation of the adsorption of five proteinogenic amino acids on calcite(104) under ultra-high vacuum (UHV) conditions. For studying the structures formed from comparatively large amino acids, enantiopure tryptophan, tyrosine and aspartic acid molecules are deposited onto the surface held at room temperature (RT). These results are compared to the structures observed when depositing the two smallest amino acids , namely glycine and alanine. Our results reveal strikingly similar island structures with a (5 × 1) superstructure for the class of large amino acids despite the rather different side chains. The chirality of the molecules is unambiguously identified by a characteristic angle that is formed with respect to the \([42\bar{1}]\) substrate direction. The structures observed for glycine and alanine, on the other hand, differ substantially from each other and also from the (5 × 1) pattern revealed for the large amino acid. Our study illustrates that identifying general adsorption principles is difficult even in the case of rather simple molecular building blocks.