Breakthrough ultrasearch technologies targeting extralarge combinatorial compound spaces are now available as alternatives to expensive de novo chemical synthesis. Several leading companies such as Enamine (), Enamine Real Space (), Freedom Space 3.0 (), ChemSpace (), and Alipheron Hyperspace available through DW vs 6.2 ( ), offer searching through > ~ 50000 millions of virtual compounds, many of them already on stock, most other for cheap-fast combinatorial chemical synthesis. , H3R 7f61.pdb 28 and H4R 7yfc.pdb 29 ) were aligned to H1R (8x5x.pdb ) and merged in different colors. Their α-helices were drawn as cylinders for clarity. Yellow cylinders corresponded to αhelices III, corresponding to H1R residues: 96-134. The top of the figure corresponds to their variable extracellular loops. Red spheres, histamine bound to H1R.