Non-linear optical imaging of protein crystals

1. A method of detecting a protein crystal comprising:

subjecting a sample comprising a protein crystal to second order nonlinear optical imaging; and

detecting a second harmonic generation signal produced by the protein crystal suitable for protein structure determination by diffraction analysis.

2. The method of claim 1 , wherein the protein crystal has a diameter of less than about 1 micron.

3. The method of claim 2 , wherein the diameter is less than about 100 nm.

4. The method of claim 1 , further comprising:

illuminating the sample with a pulsed laser light.

5. The method of claim 4 , wherein the laser light is pulsed at less than about one picosecond.

6. The method of claim 1 , wherein the sample is formed from a crystallization experiment.

7. A method for evaluating protein crystal quality for structure determination by diffraction analysis comprising:

subjecting a sample comprising a protein crystal to second order non-linear optical imaging;

detecting a second harmonic generation signal produced by the protein crystal;

comparing a forward second harmonic generated signal and a backward second harmonic generated signal of the protein crystal; and

selecting a protein crystal exhibiting a predominately forward scattering for use in crystallography.

8. The method of claim 7 , further comprising, selecting the protein crystal for use in crystallography wherein the forward second harmonic generated signal is between about 4 times and about 6 times greater than the backward second harmonic generated signal.

9. The method of claim 8 , wherein the forward second harmonic generated signal is about 5 times greater than the backward second harmonic generated signal.

10. The method of claim 7 , wherein the diameter of the protein crystal is less than about 1 micron.

11. The method of claim 10 , wherein the diameter of the protein crystal is less than about 100 nm.

12. The method of claim 7 , further comprising illuminating the sample with a pulsed laser light.

13. A method for evaluating protein crystal quality for structure determination by diffraction analysis comprising:

subjecting a sample comprising a protein crystal to second order non-linear optical imaging;

illuminating the protein crystal with a pulsed laser beam at a first incidence angle;

detecting a second harmonic generation signal produced by the protein crystal at the first incidence angle;

rotating the protein crystal to a second incidence;

detecting a second harmonic generation signal produced by the protein crystal at the second incidence angle; and

comparing the second harmonic generation signal produced by the protein crystal at the first and second incidence angle.

14. The method of claim 13 , further comprising

measuring the intensity of the second harmonic generation signal produced by the protein crystal at the first incidence angle;

measuring the intensity of the second harmonic generation signal produced by the protein crystal at the second incidence angle;

comparing the intensity of the second harmonic generation signal produced by the protein crystal at the first and second incidence angle; and

selecting a protein crystal exhibiting a lower minimum intensity for use in crystallography.

15. The method of claim 13 , wherein the diameter of the protein crystal is less than about 1 micron.

16. The method of claim 15 , wherein the diameter is less than about 100 nm.

17. A method for evaluating a crystallization experiment comprising:

subjecting a protein crystallization experiment to second order non-linear optical imaging; and

using a second harmonic generation signal to evaluate whether a protein crystal suitable for protein structure determination by diffraction analysis is present in the crystallization experiment.

18. The method of claim 17 , wherein the protein crystal has a diameter of less than about 1 micron.

19. The method of claim 18 , wherein the diameter is less than about 100 nm.

20. The method of claim 17 , further comprising illuminating the crystallization experiment with a pulsed laser beam.