Abstract
MAIN is software that has been designed to interactively perform the complex tasks of macromolecular crystal structure determination and validation. Using MAIN, it is possible to perform density modification, manual and semi-automated or automated model building and rebuilding, real- and reciprocal-space structure optimization and refinement, map calculations and various types of molecular structure validation. The prompt availability of various analytical tools and the immediate visualization of molecular and map objects allow a user to efficiently progress towards the completed refined structure. The extraordinary depth perception of molecular objects in three dimensions that is provided by MAIN is achieved by the clarity and contrast of colours and the smooth rotation of the displayed objects. MAIN allows simultaneous work on several molecular models and various crystal forms. The strength of MAIN lies in its manipulation of averaged density maps and molecular models when noncrystallographic symmetry (NCS) is present. Using MAIN, it is possible to optimize NCS parameters and envelopes and to refine the structure in single or multiple crystal forms.
Highlights
After my arrival at the Max Planck Institute for Biochemistry in Martinsried in 1988, I began working in crystal structure determination
MAIN developments have mostly been presented at conferences and provided to the users, so that the concepts and ideas could find their way into the community; the basic citation remained my PhD thesis (Turk, 1992)
MAIN is oriented to present results as three-dimensional colour images that are smoothly rotatable on the computer screen
Summary
I decided to expand MAIN from molecular-graphics software (Turk, 1988) into general crystal structure-determination software, integrating a variety of tools into a single working environment. A description of the areas of structure determination (i) display molecular models and electron-density maps, included in MAIN is presented. It is followed by the (ii) calculate various types of electron-density maps, description of two recent rather typical cases chosen to (iii) build models from scratch and extend and rebuild demonstrate the uses of MAIN. They both exploit fourfold existing models using manual, semi-automated and automated NCS. The development of programs such as ARP/wARP (Langer et al, 2008), SOLVE/RESOLVE (Terwilliger & Berendzen, 1999), Buccaneer (Cowtan, 2006), the SHELX group of software (Sheldrick, 2010) and other programs are providing increasingly complete models in increasingly integrated environments such as CCP4 (Winn et al, 2011), PHENIX (Adams et al, 2010) and HKL-3000 (Minor et al, 2006)
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