SAMSA

M. Samsa, Potentialfor Compressed Natural Gas Vehicles in Centrally-Fueled Automobile, Truck and Bus Fleet Application, Gas Research Institute, Chicago, 1991, pp. 44-61. 

SAMSA Labeled Protein with Protected Sulfhydryl... 

Figure 1.69 SAMSA is an anhydride compound containing a protected thiol. Reaction with protein amine groups yields amide bond linkages. Deprotection of the acetylated thiol produces free sulfhydryl groups for conjugation.

Add 20 pi of the stock SAMSA solution to each ml of the protein solution, with mixing. 

Remove excess reagent and reaction by-products by dialysis or gel filtration using 0.1M sodium phosphate, 0.15M NaCl, lOmM EDTA, pH 7.5. For chromatographic separation, use a desalting gel filtration support such as the Zeba desalting spin columns (Thermo Fisher) or the equivalent. The SAMSA-modified protein may be stored at -20°C until needed. 

To deprotect the acetylated sulfhydryl group of SAMSA-modified proteins, add 100 pi of 0.5 M hydroxylamine hydrochloride in 50 mM sodium phosphate, 25 mM EDTA, pH 7.5, to each ml of protein solution. 

SAMSA-fluorescein, 5- [2(and 3)-5-(acetylmercapto)-succinoyl]amino fluorescein, is a fluorescent probe containing a protected sulfhydryl group. In its protected state, the compound is unre-active. The acetyl-protecting group can be removed by treatment with dilute NaOH at pH 10.0 (Figure 9.9). The resulting free sulfhydryl derivative can be used to label thiol-reactive crosslinkers or to couple with sulfhydryl residues on proteins and other molecules. After activating... 

Figure 9.9 SAMSA-fluorescein contains a protect thiol that can be deblocked by treatment with hydroxy-lamine. The reagent then can be used to modify molecules containing sulfhydryl-reactive groups.

SAMSA-fluorescein is an orange solid compound. Dissolved in buffer at pH 9.0, its maximal wavelength of absorption or excitation is at 495 nm, while its emission wavelength maximum is 520 nm. The reagent and all solutions and derivatives made from it are light sensitive and should be stored in the dark. SAMSA-fluorescein is soluble in aqueous solutions above pH 6.0, but it can be dissolved in DMF to prepare a concentrated stock solution prior to adding a small amount to a buffered reaction mixture. 

To deprotect the acetylated sulfhydryl, dissolve the desired amount of SAMSA-fluorescein (Invitrogen) in lOOmM NaOH, pH 10.0, at a concentration of lOmg/ml. 

There are other kinds of criteria that do not focus on specific medications but rather on the patient. One such example is Medication Appropriateness Index (MAI) with different questions as e.g. Is there an indication for the drug (Samsa et al. 1994). This instrument may be more useful when assessing pharmacotherapy for the individual patient. 

Libscomb J, Ancukiewicz M, Parmigiani G, Hasselblad V, Samsa G, Matchar DBJ. Predicting the cost of illness a comparison of alternative models applied to stroke. Med Decis Making 1998 18 S39-56. 

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