Direct insertion membrane probe

Mendes, M.A. and M.N. Eberlin. 2000. Trace level analysis of VOCs and semi-VOCs in aqueous solution using a direct insertion membrane probe and trap and release membrane introduction mass spectrometry. Analyst 125 21-24. 

Although the techniques of HPLC, GC, and mass spectrometry (MS) (Christiaens et al., 2004 Sanhueza et al., 1996) are very efficient, mainly when coupled with other methods, the FIA online system has been used successfully to determine acetic acid concentrations. Teeter et al. (1994) adapted a direct insertion membrane probe in mass spectrometer and the analytes of interest pass through the membrane and are ionized by electron implant ionization. The technique is cost effective and simple to implement, especially when used with an ion trap mass spectrometer. The high cost of acquisition of the equipment required explains the small number of studies employing online FIA and the preference for the use of photometric techniques together with an FIA system. 

FIGURE 4.1 (a) MIMS systems with direct membrane sampling and (b) direct insertion probe in MS... 

One experimental tool in this direction is provided by some enveloped animal viruses which mature at the cell surface of infected cells (K Sri inen and Renkonen, 1977 Lenard, 1978). Such viruses include influenza virus, Semliki Forest virus (SFV), Sindbis virus, and vesicular stomatitis virus (VSV). They are extremely simple in makeup and hence are very well characterized. They can be tagged with biochemical probes in many different ways. They infect many animal cells in culture, and after infection turn the cells into factories for the production of virus progeny. The protein-synthesizing machinery of the host cell is programmed by the viral RNA to make viral proteins exclusively and these include the viral surface glycoproteins. These are synthesized with signal peptides and inserted into the ER membrane (Katz et ai, 1977 Garoff et... 

Printed membranes were hybridized with a purified 600 bp GAPDH insert and labeled with radioactive probes. Visible signal was detected after 5 min of exposure with a digoxigenated probe followed by 30 min incubation with the radiolabeled probe. Mock hybridization experiments verified that there was no observed, unspecific signal, confirming that inkjet printing using standard desktop printers can be used to directly transfer DNA onto membranes for further reactivity. 

Experiments primarily from the laboratory of Aripov on a CTX isolated from Asian cobra venom also show a direct CTX interaction with phospholipid bilayers. Using spin label probes,the CTX (designated cytotoxin was shown to partially insert into phospholipid bilayers to cause an increase in the order parameter of PA liposomes (58). The CTX also interacts with PC/PS liposomes to cause aggregation, increased membrane permeability and enhanced fusion (59). Insertion of CTX into a PC bilayer containing 10% PA was also shown by x-ray small angle scattering (60). 

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