The Applications Of Raman Spectroscopy In The Identification Of Dna, Protein Detection And Ink

Acid at various pH have different effect on organism. In medical science, tumors once directly have been treated by acetic acid and applied to clinical patients. All this have gotten wonderful achievements. So they are meaningful works which study, the molecule conformation change of DNA and protein on the condition of acid at various pH. By Raman spectroscopic technique, we have studied the molecule conformation change of DNA of calf thymus with acid at various pH and at the same pH after different time. We also researched the effects of molecule conformation of lysozyme solution treated with acid at various pH. Besides, we have identified the types of the ink marks of the gel ink pen and blue ball pen. And we have done this work for the Discrimination Center of Material Evidence. Revolving around three aspects above, we have done the following works:1. The Raman spectra of DNA in acidic solution divided into pH6.0,pH5.0s pH4.0,pH3.0,pH2.0 and pH1.0 were measured. The results showed that protonation of DNA occurred and the Raman characteristic shifts and these intensities were changed in different degree for various pH values. With the acid increased, the conformation of DNA also changed.2. The Raman spectra of DNA in acidic solution at pH3.0,pH2.0,pH 1.0 after 1 h,2h,12h,24h were measured. The results showed that protonation of DNA occurred and the Raman characteristic shift and intensity were changed in different degree at various pH and after different time. The protonation of DNA changed gradually deeper from pH3.0 to pH1.0. Up to pH1.0, the conformation of original double helix was modified and changed.3. The Raman spectra of lysozyme solution treated with various pH (from pH5.0 to pH1.0) have been measured. Thus all the characteristic Raman bands of the protein proved that their structure consist of theα-helix and random coil. In the procedure of acidity, the conformation of lysozyme would keep stable, but at pH <2.0, the lysozyme begin to denature. At pH5.0, the tyrosine residue are "exposed", at pH4.0～　pH2.0 the tyrosine residue are "buried", at pH1.0, the Raman bands of the tyrosine residue almost have vanished. The intensity of the 1361 cm^-1, peak in tryptophan decreases with increase in acidity and slowly change from "buried" to "exposed". The Raman bands of the disulfide bridge C-C-S-S-C-C appear at 508, 508, 507, 507 and 509 cm^-1, and their intensities almost do not change. As can they indicated, in the environment of acid, the conformation of the disulfide bridge S-S always is gauche-gauche-gauche.4. The Raman spectra of different brands' ink marks by spectroscopic technique were measured. All Raman spectra were excited with 325nm and 514.5nm radiation. With 514.5nm radiation, the ink marks of black and blue ball pen have a lot of Raman spectra, but the Raman spectra of the gel ink pens only have bands of carbon. At the same time, tuned to 325nm as the exciting line, lots of clear Raman spectra appeared. It is indicated that the distinctiveness of Raman spectra of ink marks of the same kind and different brand's pens existed.5. We take part in the job on inkblot discrimination with discrimination center of Police Bureau of Jingsu Province and discrimination center of Nanjing Normal University. With the technology of Raman spectroscopy we identify the different kinks of inkblot in the texts or notes. For the characteristics of accurate dates of experiments and non-destructive to sample, the job has been admitted by the workers in the centers, providing the enough scientific proof for the sentence of the court.