that the time rrquirrd to complete all the rimulnr~onswas excessive. F:wn when the srmulntlons are dune at the highest spcrd, it takes one t o two minutes to obtain each saturation point. I t would be helpful to have the option of speeding up the simulation even more. The simulation progresses by exploring how the addition of COr. . a o H chanee. and 2,3-DPG cwwntration affect\ the 0, saturationcurve The effect uf COun Or h:nding by hemoglobin is examined. The saturation curve for myoglobin is obtained and compared to that for hemoglobin. The different saturation curves are graphed in different colors and can be compared on the same graph. The concepts of eaoperativity and allosteric proteins are introduced by questions in the workbook. The proportional size of hemoglobin t o the 0 2 molecules is not realistic, but the workbook points this out and explains that moleit is necessary in order to make the 0% cules visible in the simulation. The symbols for hemoglobin are only diagrammatic; the polypeptide backbone and heme groups are not shown in detail. Such a picture of the four subunits and the accompanying change in quaternary structure upon Oz binding as revealed by the X-ray studies of Max Perutz would be a valuable teaching tool. The dynamics of three-dimensional structural changes are extremely difficult to visualize on the printed page. The resolution of the Aoole . . comouter makes that a difficult oroo. . u r l r ~ mAs . stated by the author, the locusof this ~imulntioniz on thr iunrrion of hrmoglubinnnd not on its strucrurc although thr concepts go hand in hand. As microcomputer resolution and memory increase, undergraduate students may soon have access to three-dimensional images of proteins a t the molecular level. The program can be recommended as a helpful supplement to understanding the concepts of cooperativity and allosteric proteins, although the above mentioned limitations should be kept in mind. The six students who completed the entire workbook spent between two and four hours a t the terminal. Students thought the program was helpful in understanding the concepts although they complained about the time required to complete the individual simulations. Whether the program is worth the price depends on what emphasis the instructor places on the comprehension of these concepts by students. David Roll Roberts Wesleyan College 2301 Westside Drive Rochester. NY 14624
.
Review II Simulation ofHernoglobinFunction isan instructional package consisting of a single disk and a workbook. The author's objectives are t o provide students with a feeling for molecular dynamics by showing qualitatively and quantitatively the function of myoglohin and hemoglobin. He attempts to show the effects of certain small molecules and other species on hemoglobin function and provides the instructor with a package
A114
Journal
of Chemical Education
that can be used individually or as a classroom demonstration. Familiarity with the basics of hemoglobin and myoglobin structure and function prior to using the software is anticipated by the author. The program is easy to use with no obvious errors that could cause interruotions. There are clear dwctions for booting the disk and using the uurkbouk and nu prior knowledge of computer, is required. A glossary of all commands used to control the program is found in the workbook. In our department, the program was reviewed by four senior undergraduate biochemistry majors, a graduate student, a biochemistry professor whose primary research relates to hemoglobin function, and myself (the coordinator for our biochemistry undergraduate program).
tors might like to add this facility, hut the authur did nut dercrihe an easy way for the program to be modified. As no prior knowledge of computers is necessary, students had no trouble using the software without supervision. A colored model of the molecules is on the screen a t the same time as a graph; however, one student pointed out that the molecules should be in different shapes, along with different colors, so that black and white monitors can also be used. Most students enjoyed using the workbook, but some found the questions a little oversimplified. (i.e.; press a key, now write down what happens.) Beginning college students and high school students would probably not he insulted by such instructions. Our upper level undergraduates were.
Subject Matter The program is offered as a supplement t o more traditional methods of teaching and provides a list of references that may he useful. The software generates a screen that is divided into quadrants, with an animated eraohic deoictine hemoelobiu subunits and " active small molecules (such asoaveen.. CO,... and 60, Louncing around. Anothrr arra of thescreen provides agraph of prrcrnt saturation versus POP (or COX,or CO). The student can vary the gas concentration by using the keyboard and this willcreateaehange in the percent saturation and will also show a corresponding change in the number of gas molecules in the animation. In this particular case, as the number of oxygen molecules increases there is a resulting change in the hemoglobin T or Rstate. Students may also vary the rate of the reaction, which affects the resulting hemoglobin state. The function of hemoglobin in the presence of 2,3diphosphoglycerate (DPG) is also described. In summary, students can control the small molecules' concentrations and observe hrdh n llnegrnph %honingperrmt saturatam and the resulting alferts on hemutlf cmtnd pmvides glubin states. T h ~ iype i students with an opportunity to enhance their understanding of the functional relationship hetween hemoglobin and small molecules such as 02, COz, and CO. A few areas should be clarified in the procram. The removal of DPG modifies affinitv hut DPG remmnl d r m not r ~ d u r ecouperntrwry. although the pnwnm stnrea that it does. Also, this program demonstrates a model far hemoglobin, but there is no explanation for how this model is constructed. Underlying kinetic assumptions, choice of rate constants, etc. should be explained. Instructors and uooer level undereraduates shuuld be ahle tc, underitand suchan explnnatiw. This cwld have been g:wn in the u,orkbook, ii not in the suftware In drmunsrrnting the ~tarisricalmechanicsof rooprratlrlty. the author uses the expwssi~n"Or rmpernrwity", which is nn tuntnmilior term
The author should consider expanding the workbook to include more background about the "model" being demonstrated, emphasizing the fact that it is one model and explaining how this model is constructed. Paints related t o the reduction in cooperativity and percent cooperativity should be clarified. The oroeram .. itself could be impmved hy altering 11 w t h a t aftergeneration of the fir51 line on the graph, lurthrr iinrs could be getaerated mow quicklv.
". ~
~
.
~~~
~
~~~
~
-~
~
~
Recommendations for Improvement
.
Summary This program has effectively combined the interactive nature of computer-assisted instruction with an animated graphic to demonstrate the dynamics of molecular interaction. Because the author has succeeded in his stated goals, it should be a valued instructional tool. althoueh the use of this program will he limited I
