Robert 1. Pecsok
University of California Los Angeles, California 90024
A New Approach to the Sophomore Course "Biorganalytical" chemistry at UCLA
N o one will question that the rapid advances in chemistry have completely revolutionized graduate training in the last decade or two. Much of what was formerly "graduate-level" work must now be covered in the undergraduate curriculum, or the student will never be able to reach the frontiers. At the other end of the line, teaching in the secondary schools is becoming more sophisticated, and with continued emphasis on the new chemistry programs (CHEMS, CBA, and related developments), our entering freshmen are surely better prepared than ever before. Recent freshmen texts reflect this-a careful study of some of them will reveal at least as much if not more material than was in an entire bachelor's degree program not too many years ago. Pressure is developing at both ends of the educational spectrum. Analytical chemists have traditionally taught the elements of good laboratory technique, including p e tience, precision, and meticulous attention to detail; and just as "you can't hurry a good stew," neither can you do a quick quantitative gravimetric chloride. But as the Scientific Revolution gathers speed, we may already have passed the time when analytical chemists can be given the luxury of the sophomore year, or even a separate semester, to teach chemical principles and techniques around a core of analytical procedures which are seldom used after the course is finished. This has been recognized by many departments, and the most common approach seems to involve an integration of the elementary analytical course into the general chemistry course, with a consequent de-emphasis of analytical chemistry a t many institutions. We are offering a new and, we believe, unique combination of analytical material. The UCLA Chemistry Department has taken advantage of the change in University calendar from the semester to the quarter system to make significant changes at all levels. but the most imuortant chanee is the introduction of new program fog the second year. A series of three half-courses will give a modern introduction to organic and biochemistry. A concurrent series of three half-courses provides a modern introduction to analytical methods of organic and biochemistry (with both lectures and laboratory). Although we have arbitrarily called the first two quarters 'Lorganic" and the third "biochemistry," the program would work equally well with a semester calendar. It is not even essential that the analytical course be concurrent with the organic lecture course--it could just as well follow
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Presented a t the Joint Symposium on The Teaching of Analytical Chemistry a t the 152nd Meeting of the American Chemical Society, New York City, N. Y., September, 1966.
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it. Thus, the two most novel features of our curriculum which we shall expand in this discussion are: (1) The requirement of a biochemistry course in the lower division. (2) The introduction of modern laboratory techniques and analytical methods of organic and biochemistry as a unified combination, "biorganalytical" chemistry.
Both chemistry and life-science majors will take the first two years of our program. The Role of Biochemistry
In our view more than a token amount of biochemistry belongs in the chemistry curriculum, and it should he introduced as a required subject as early as practicable. A majority of our students in the first two years are non-majors, most of whom are oriented toward the life sciences. Chemistry majors themselves are turning more and more to biochemistry, a very natural development as they too can read and learn that here is "where the action is!" Biochemistry is in a period of rapid expansion and its dynamic character can well be used to stimulate undergraduates a t the threshold of their studies. This is especially true for non-chemistry majors who have long wondered (rightfully) why they should he excited about complex equilibrium problems so dear to analytical chemists. The teaching of equilibrium principles can be enriched by taking examples from amino acids or physiological buffers. The third quarter lecture course with some 20 meetings of the class will give the student not only an introduction to the principles and practices of biochemistry, but also an insight into the exciting frontiers that concern biochemists. The Role of Analytical Chemistry
Analytical chemistry plays a key role at some stage of almost all laboratory work in every area of chemistry, whether inorganic, organic, physical, or biological, Thus the teaching of analytical chemistry should emphasize all of these applications in an integrated fashion rather than merely the traditional field of inorganic quantitative analysis, Analytical chemistry includes a study of the principles, tools, and techniques used for all chemical measurements regardless of whether the end result is a determination of composition, structure, reaction mechanism, or any other property, The classical techniques of gravimetric and volumetric analysis are treated effectively when presented to freshmen who are challenged by the material. Provided with first class equipment, a good freshman can
work a t the *0.1% level just as well as a t the c u e tomary 10.5% level. The new analytical chemistry course for sophomores resembles neither classical quantitative analysis, nor traditional organic, nor biochemistry. It is, in fact, a marriage of the several sub-disciplines, each of which complements the others. The student is met with material for which he can see immediate application. For example, in organic lectures he is introduced to structure-physical property correlations. In lahoratory, he uses differences in physical properties to separate, detect, and measure amounts of organic or biological compounds. Analytical Methods of Organic and Biochemistry
This is the title of a new half-course lasting three quarters in each of which there are 20 lectures and 10 four-hour laboratory periods. About 500 students a year will pass t,hrough this course of whom 8W.100 are chemisdry majors. A single 4-hr laboratory per week is nearly as effect,ive as two 3-hr laboratory periods, and makes it possible to have a maximum of 48 students (two rooms of 24 each) at any given time. This is in line with our objective to provide equipment wherever possible so t,ha,t the student can do the experiment himself. First Qwlrter. The course begins with a consideration of the melt,ing point (range) as a means of identification as well as a criterion of purity. Determination of the melting point is about as simple a procedure as one can perform, yet the theory of the phase change includes the first use of thermodynamics. Melting point-composition curves lead into zone refining, one of the most elegant and powerful separation techniques for solids. The study of melting point also provides the hackground for the analogous study of the boiling point. Phase diagrams for a number of kinds of systems (pure substances, solutions, azeotropes) are plotted in several ways providing the background for separation by fractional distillation. The comparison of a pseudobatch type distillation in a bubble cap column with true continuous distillation in a packed column is a means of introducing the "theoretical plate" concept. The next topic, extraction, introduces the idea of a distribution coefficient. There is an obvious progression from single to multiple extraction and finally to the automatized Craig machine and continuous countercurrent extraction in a column. By now all the background for chromatography has been covered. Chromatographic theory is discussed in some depth for gas-liquid chromatography with emphasis on the factors that determine retention and the factors that determine band spreading. The details of the various kinds of chromatography are then easily provided by a simple change in the nature of the phases, the mechanism of the distribution, the means of detection, and the geometry of the apparatus. The second major topic is spectroscopy, and in the remainder of the first quarter we take up the nature of electromagnetic radiation and its interaction with matter, along with application in the visible, ultraviolet, and infrared regions. We emphasize spectral interpretations and spectra-structure correlations. Second Quarter. Continuing the theme of spectros-
copy, the first topic taken up in the second quarter is nuclear magnetic resonance including a simplified explanation of chemical shift, spin-spin coupling, and nuclear relaxation. Although mass spectrometry is more properly a separations technique than a form of spectrometry, it does yield a spectrum related to structure; it is fingerprint technique. Here again, spectral-structure correlations are emphasized; in a qualitative fashion the cracking pattern is related to reactivity. As a third broad topic we take up the more fundamental and more quantitative subjects of electrochemistry and acid-base chemistry. However, the electrochemistry is geared to developing an operational definition of pH (with the glass electrode and pH meter) and to the development of coupled oxidation-reduction reactions so that some of the biochemical energy transfer mechanisms can be discussed. The treatment of acid-base equilibria is directed toward the understanding of amino acid equilibria and buffers of physiological importance. Concepts of acidity are developed for nonaqueous as well as aqueous solvents; and again, the effect of structure on acidity is treated in detail. The chemistry of chelate formation is similar to neutralization; in both, a coordinate covalent band is formed from a pair of electrons donated by one atom. Chelates are first introduced in the interpretation of spectra (ligand field theory) in the first quarter, and discussed again following acid-base chemistry in the second quarter. Biochemical examples of chelation will be considered further in the third quarter. Kinetics, likewise, appears throughout the course, hut rate expressions per se for simple reaction types are covered as a topic in the second quarter. Third Quarter. The last third of the course concerns analytical methods of biochemistry. To be sure, all of the methods used here have already been discussed in the first two quarters or in the freshman course. I n a sense this quarter is a review of methods with biochemical applications. It will be more than a review for the large numbers of students who transfer to UCLA after two years elsewhere; it is expected that most of them will enter our curriculum a t this point. The student will soon learn how to handle enzymes and other macromolecules in amounts that are too small for ordinary detection methods. The course begins with a study of the rate and mechanism of ester hydrolysis catalyzed by acid and by an enzyme. The kinetics of the two systems are compared to show the effectiveness of enzyme catalysis. The reactions are followed with a spectrophotometer in the ultr* violet region. Next the kinetics of an oxidation reaction, the oxidation of NADH with pyruvate is studied using the Michaelis-Menten treatment of the data. Separations are reviewed by considering the ion exchange behavior of amino acids and the gel filtration of ovalbumin. The amino acid separation is followed by paper chromatography, while the gel filtration is followed by the use of ovalhumin tagged with radioactive 13'I. Further experience in handling radioisotopes is provided by measuring the phosphorylase-catalyzed cleavage of glycogen with 32P-phosphate. The size and degree of branching of glycogen is also Volume
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determined by periodate oxidation. The number of strands in the DNA helm is determined by measuring the viscosity of a DNA solution as a function of time during enzymatic degradation. The dependence of the native DNA duplex structure upon ionic strength and temperature is also studied, again using viscosity studies. The Laboratory. A list of laboratory experiments for the Analytical Methods course is given in the table. At first sight it may appear that the cost of equipment is prohibitive; however, with a maximum of 48 students a t a time, we will be able to provide each student with standard-taper glassware, chromatographic equipment for thin-layer, paper, ion exchange, and column separations. Each student will have his own pH meter, but other instruments which are used only part of the time will be provided only for pairs of students (for example, radiation counting equipment, gas chromatographs, and Spectronic 20 spectrophotometers). An inexpensive, yet rugged, reliable, accurate, and sensitive gas chromatograph has been developed for educational purposes. Its plumbing and wiring can be readily exposed and inspected, so that a t least in this instance, the "black box" is avoided. The total cost of the instruments used in this course (exclusive of glassware and normal desk equipment) is $68,800. For 48 students at a time, this is $1440 per student station. Each station is used 10 times per week by 10 different students, thus the cost per student is less than $150. Most of this equipment is durable and can be used for many years. It is suitable for many undergraduate research problems.' We have stopped short of providing infrared spectrophotometers, nmr spectrometers, and mass spectrometers for the individual student. For these techniques we will rely on films, TV tapes, and the like to give the student a feel for the use of the instrument. Some excellent films are already available. The department, with the cooperation of our Theater Arts Department, has produced a film which provides an introduction to the theory and practice of nmr. The courses described are being given for the first time in 196647. We have already generated much excitement among students, faculty, and colleagues in 1 We are grateful to the National Science Foundation for a Grant (GY-1952) for partial support of this program.
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the life sciences. We hope that the excitement reflects more than just the novelty of our program. I t should bring chemistry in the lower division much more in line with "what chemists do," and present a much more attractive picture of our subject. Laboratory Program of Chemistry 6ABC Analvticol Methods of Oraanic and Biochemistrv
First Quarter Determination of meltimg points. Separation by extraction of a two-component mixture with identification by melting point. Separation by fractional distillation with analysis of fractions by gas chromatography. Separation by column (adsorption) chromatography with analysis of frttctions bv thin-laver chromstoera~hv. Study of a charge-transfer complex by spectrophotometry in the visible region. Study of infrared spectrophotometry (by film) and the interpretation of selected infrared spectra. Second Quarter Study of nuclear magnetic resonance spectrometry (by film) and the interpretation of selected nmr spectra. Study of mass spectrometry (by film) and the interpretation of selected mass spectra. Interpretation of combined spectra (nv, ir, nmr, and ms) for selected compounds. Study of phosphate buffers with the pH meter. Acid-base titrstions in nonaqueous solvents; the determination of nicotine in tobacco. Kinetics of methanolysis of an ester followed by gas chromatography. Third Quarter Reaction kinetics of acid-catalyzed and chymotrypsin catalyzed saponification of p-nitrophenyl acetate followed by uv spe* trophotometry. Reduction of pyruvate to lactate (hydride ion transfer) catalyzed by nicotinamide adenine dinucleotide followed by spectrophotometry; determination of Michaeli constant of pyruvate. Separation of amino acids by ion exchange followed by paper chromatography. Determination of Geiger counter charttcteristics. Isolation of '%tagged ovalhumin by gel filtration followed by radioactive counting. Kinetics of degradation of DNA solutions followed by viscosity to determine number of strands. Study of phosphorylsse catalyzed cleavage of glycogen followed by =ZPlabeling. Oxidahon of glycogen with periodate to determine end groups and branching followed by pH titration.
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