ESI

ESEM environmental scanning electron microscope ESI electron spectroscopic imaging... 

For a detailed discussion on the analytical teclmiques exploiting the amplitude contrast of melastic images in ESI and image-EELS, see chapter B1.6 of this encyclopedia. One more recent but also very important aspect is the quantitative measurement of atomic concentrations in the sample. The work of Somlyo and colleagues [56]. Leapman and coworkers and Door and Gangler [59] introduce techniques to convert measured... 

Dor esi R, C Pisani, C Roetti and V R Saunders 1983. Treatment of Coulomb Interactions in Hartree-Fock Calculations of Periodic-Systems. Physical Review B28 5781-5792. 

Electrospray ionization (ESI) produces a series of multicharged ions that can be transformed into an accurate molecular mass for proteins with masses of tens of thousands. 

Peptides and proteins can be analyzed by mass spectrometry. Molecular mass information can be obtained particularly well by MALDI and ESI. 

Fig. 9. Mass spectra of lyso2yme having 14,305 mol wt. See text, (a) Isims spectmm (b) ESI spectmm (1). Courtesy of Kratos Analytical.

Another big advance in the appHcation of ms in biotechnology was the development of atmospheric pressure ionization (API) techniques. There are three variants of API sources, a heated nebulizer plus a corona discharge for ionization (APCl) (51), electrospray (ESI) (52), and ion spray (53). In the APCl interface, the Ic eluent is converted into droplets by pneumatic nebulization, and then a sheath gas sweeps the droplets through a heated tube that vaporizes the solvent and analyte. The corona discharge ionizes solvent molecules, which protonate the analyte. Ions transfer into the mass spectrometer through a transfer line which is cryopumped, to keep a reasonable source pressure. 

Prior to the introduction of ESI, ms /ms studies of peptides were generally limited to molecules mol wt < 3500 (33). This limitation was a consequence of the rapid drop in precursor ion intensity from Isims ion sources with increasing mass, and the inefficiency of coUisional activation. Good... 

Uracil, 6-amino-1-benzyl-5-nitroso-2-thio-syn esis, 3, 131 Uracil, 6-amino-2-thio-synthesis, 3, 115 Uracil, 1-benzyl-syn esis, 3, 109 Uracil, 1-benzyloxy-... 

Esi-ms measurements were performed on a Agilent LC M,SD system with the following operational parameters capillary voltage 4.0 kV, cone voltage, 50 V and solvent flow (methanol - water, 50% v/v) 0.3 inL/min. All esi mass specttal data in the positive ion mode were acquired and processed using HP Chem.Station software. The concenttation of aluminum was 0.5 mmol dm while that of mfx were varied in the interval 0.5-1.0 mmol dm. The pH values were pH 4.0, 6.0, 7.2 and 8.5. The specttum obtained at A1 to mfx concenttation ratio 1 2 and pH 4.0 is shown in Fig. 1. 

Fig. 1. Esi-ms spectinm of aliuniniun-moxifloxacin solution. C, = 0.5 mmol dnr, C, =1.0 mmol dnU,...

Rubijervine (slanid-5-ene-3 -12a-diol) [79-58-3J P Esi -7.0. Crystd from EtOH. It has solvent of crystn. 

P Esi 7.9. Redistd, dried under high vacuum over 24h, and stored under nitrogen. 

---