MPI MODULAR SYSTEMS

Announcing 5 New Precision Plug-In Units

MP-1004A Log Ratio Amplifier. 6 decades range: 10 3 to 10 ' A. 100 mv/decade out­put. Built-in reference gives log of single input. Accepts positive or negative inputs.

MP-1030A High Voltage Power Supply. -500 to - 1500 V. Adjustable current limit protects PM tubes. 3 operating modes: fixed voltage, programmable voltage and constant PM current.

MP-1039 Dual, FET Operational Ampli­fiers. Input current typically 3 pA at either input. 1012 ohms resistance at either in­put. Open loop gain 2x104 minimum. 6V//isec slew rate.

MP-1040 Multiplier. Seven switch selected functions: A710; AxB/10; 10A/B, B > 0 ; 10A/B, B < 0 ; V - B , B < 0 ; VB, B > 0 . Four quadrant multiplier.

MP-1041 Instrumentation Amplifier. Pro­vides gains from 1 to 1000. Range switch and 10-turn potentiometer. Input impe­dance, differential and common mode, 10,! ohms typ. Guarded inputs.

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na tura l ly occurring proteins , usual ly n o n i m m u n e globulins, which have specific affinity for the hormone or a class of hormones . E x a m p l e s include m a n y steroid hormones , thyroxine, v i t amin D3 and its metabol i tes , and v i t amin B12. The rad ioenzymat ic assay employs an enzyme as t he reac­tive agent , and the separa t ion of two radioact ive pools involves separa t ion of two compounds , one of which was formed from the other by the enzy-mat ical ly cata lyzed react ion. An ex­a m p l e is t he folic acid assay by use of folic acid reductase . T h e radiorecep­tor assay employs a par t ia l ly purified t issue receptor as the react ive agent . Examples include adrenocort icotropin (ACTH) , cyclic A M P , and cyclic G M P . T h e immunorad iomet r i c assay differs from the RIA and other re la ted methods . It uses a radioact ively la­beled purified an t ibody . Unreac ted and reac ted labeled ant ibodies are sep­ara ted by adsorpt ion to ant igen which is bound to a solid suppor t . Examples include insulin, growth hormone, calcitonin, and para thyro id hormone .

Generally, the RIA has numerous advan tages over related methods . Compared to C P B , RIA has greater sensit ivity and specificity, so t h a t the specimens do no t require chromatog­raphy or o ther purif ication s t eps . T h e radioreceptor assay is res t r ic ted to compounds for which t issue receptors can be identified and isolated, al­though they do have one advan tage of measur ing "biologic ac t iv i ty" as op­posed to " immunologic ac t iv i ty ." However, if t he RIA is properly vali­da ted , there is no essential difference. T h e rad ioenzymat ic assay m a y be able to measure compounds for which ant ibodies cannot be readily m a d e bu t has the d i sadvan tage of requiring separa t ion of compounds of s imilar size a n d s t ruc ture for quan t i t a t i on . T h e immunorad iomet r i c assay does not have some of t he " b l a n k " prob­lems of the RIA b u t is costly in its use of an t i se rum and ant igen and is more difficult to set u p initially.

Bibliography The first section includes a number of

reviews, symposia, and workshops on ra­dioimmunoassay and related methods. The additional sections include references on specific subjects, although most of the references in the General section also cover these topics.

General 1. S. A. Berson, R. S. Yalow, S. M. Glick,

and J. Roth, Immunoassay of Protein and Peptide Hormones, Metabolism, 13, 1135(1964).

2. S. A. Berson and R. S. Yalow, Immu­noassay of Protein Hormones, in "The Hormones," G. Pincus, K. V. Thimann, and E. B. Astwood, Eds., Vol 4, pp 557-630, Academic Press, New York, N.Y., 1964.

3. J. T. Potts, Jr., L. M. Sherwood, J. L.

H. O'Riordan, and G. D. Aurbach, Ra­dioimmunoassay of Polypeptide Hor­mones, Advan. Int. Med., 13, 183 (1967).

4. S. A. Berson and R. S. Yalow, General Principles of Radioimmunoassay, Clin. Chim.Acta, 22,51 (1968).

5. E. Diczfalusy, Ed., "Immunoassay of Gonadotrophins," Acta Endocrinol., 63, Supplementum 142 (1969).

6. M. Margoulies, Ed., "Protein and Poly­peptide Hormones," Part 1, Excerpta Med. Int. Congr. Series No. 161, Am­sterdam, the Netherlands, 1969.

7. Β. Ε. P. Murphy, Protein Binding and the Assay of Non-Antigenic Hormones, Rec. Progr. Harm. Res., 25, 563 (1969).

8. E. Diczfalusy, Ed., "Steroid Assay by Protein Binding," Acta Endocrinol., 64, Supplementum 147 (1970).

9. G. H. Grant and W. R. Butt, Immuno­chemical Methods in Clinical Chemis-trv, Advan. Clin. Chem., 13,383(1970).

10. J. W. McArthur and T. Colton, Eds., "Statistics in Endocrinology," MIT Press, Cambridge, Mass., 1970.

11. F. G. Peron and B. V. Caldwell, Eds., "Immunologic Methods in Steroid De­termination," Appleton-Century-Crofts, New York, N.Y., 1970.

12. W. D. Odell and W. H. Daughaday, Eds., "Principles of Competitive Pro­tein-Binding Assays," Lippincott, Phila­delphia, Pa., 1971.

13. K. E. Kirkham and W. M. Hunter, Eds., "Radioimmunoassay Methods," Churchill Livingstone, Edinburgh, Scot­land, 1971.

14. A. R. Midgley, Jr., G. D. Niswender, V. L. Gay, and L. E. Reichert, Jr., Use of Antibodies for Characterization of Gonadotropins and Steroids, Rec. Progr. Horm. Res., 27.235(1971).

15. D. S. Skelley, L. P. Brown, and P. K. Besch, Radioimmunoassay, Clin. Chem.. 19,146(1973).

Principle and Treatment of Data 16. G. Scatchard, The Attraction of Pro­

teins for Small Molecules and Ions, Ann. N.Y. Acad. Sci., 51, 660 (1949).

17. D. Rodbard, P. L. Rayford, J. A. Coo­per, and G. T. Ross, Statistical Quality Control of Radioimmunoassays, J. Clin. Endocrinol. Metab., 28, 1412 (1968).

18. R. Ekins and B. Newman, Theoretical Aspects of Saturation Analysis, Acta Endocrinol., 64, Supplementum 147, 11 (1970).

19. R. S. Yalow and S. A. Berson, Ra­dioimmunoassays, in "Statistics in En­docrinology," J. W. McArthur and T. Colton, Eds., pp 327-44, MIT Press, Cambridge, Mass., 1970.

20. W. G. Duddleson, A. R. Midgley, Jr., and G. D. Niswender, Computer Pro­gram Sequence for Analysis and Sum­mary of Radioimmunoassay Data, Corn-put. Biomed. Res., 5, 205 (1972).

Antiserum Preparat ion and Evaluation 21. J. Freund, The Effect of Paraffin Oil

and Mycobacteria on Antibody Forma­tion and Sensitization, Amer. J. Clin. Path., 21,645(1951).

22. G. D. Niswender and A. R. Midgley, Jr., Hapten Radioimmunoassay for Ste­roid Hormones, in "Immunologic Meth­ods in Steroid Determination," F. G. Peron and B. V. Caldwell, Eds., pp 149-73, Appleton-Century-Crofts, New York, N.Y., 1970.

23. B. A. L. Hum and J. Landon, Antisera for Radioimmunoassay, in "Radioimmu­noassay Methods," Κ. Ε. Kirkham and W. M. Hunter, Eds., pp 121-42, Chur­chill Livingstone, Edinburgh, Scotland, 1971.

24. W. D. Odell, G. A. Abraham, W. R. Skowsky, M. A. Hescox, and D. A. Fish-

888 A · ANALYTICAL CHEMISTRY, VOL. 45, NO. 11, SEPTEMBER 1973