Nonlinear optical methods such as second harmonic generation (SHG) and two-photon excited UV fluorescence (TPE-UVF) imaging are promising approaches to address bottlenecks in the membrane protein structure determination pipeline. The general principles of SHG and TPE-UVF are discussed here along with instrument design considerations. Comparisons to conventional methods in high throughput crystallization condition screening and crystal quality assessment prior to X-ray diffraction are also discussed.
Keywords: Crystal detection; Crystal optimisation; Crystal positioning; High-throughput screening; Microscopy; Nonlinear optical microscopy; Second harmonic generation; Two-photon excited UV fluorescence.