Linked-Atom Least-Squares program

For electron diffraction of the unpolymerized dimer, microscopic single crystals were obtained from a dilute hexane solution at 4 C. The structure refinement was carried out using the linked atom least-squares (LALS) program (developed by Arnott and coworkers (12) ) on 19 unique reflections. The unit cell Is... 

The Linked Atom Least Squares (LALS) program (18,19) by Arnott and coauthors is used at several institutions, including Purdue, where it was developed, and Case Western Reserve University, where it was used by Gardner and Blackwell. It is best Implemented on a large computer the Control Data Corporation supercomputer at Purdue handles it very rapidly. Setting up a new model with LALS is more complicated than with the other programs, but LALS appears to provide realistic molecular flexibility. 

Molecular Model. Amino acid analyses of all these three silk fibroins show a uniformly high content of alanine ([Ala] ). There is an option in linked-atom least-squares (LALS) program to indicate two molecular chains by defining the constraints for only one of them. Here, the geometry for Ala is for the D-Ala and not L-Ala. The molecular conformation must satisfy both the sterical and mathematical requirements. Hence, we have chosen initial

main chain was constructed with appropriate helical parameters together with bond lengths and angles. 

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