- Email: [email protected]
How Importants is Question Sequence?
164 The author concludes that, provided the test is constructed in such a way as to avoid the hard-to-easy sequencing of test items, there is little benefit in expending effort on careful item sequencing by difficulty.
Monitor CHARLES F A BRYCE
Department of Biological Sciences Napier College of Technology Edinburgh, Scotland
[Department of Education, University of Auckland, Auckland, New Zealand]
BTEC Projects in the Areas of Biochemistry and Chemistry.
Marfey, P and Klein, L Can We Learn Anything from Simple
BTEC Higher National Courses. Code No 09-031-6, pp 19 (1986)
63, 975-976 (1986)
Mechanical Models of Globular Proteins? J Chemical Education
This is a set of guidelines prepared by the Board for Science of the Business and Technical Education Council (BTEC) intended for project supervisors on BTEC Higher National Courses but it will certainly be of much wider use. Many of the points made are common sense but this does not detract from the text since there are many useful tips and all of the issues surrounding the design, implementation and assessment of student projects have been collected and distilled in a single brief document. The authors describe the characteristics of projects including staff and student responsibilities, the identification of suitable projects which should not have unrealistically high academic content, should not involve overly complex apparatus or techniques and which need not necessarily be original. A checklist is given of contributions expected of students, considered under nine headings. On assessment, the authors suggest that a distinction be made between the practical work and the project report per se and that further subdivision might also be helpful. The organisation of projects is discussed with practical suggestions which may help in the running of individual or group projects, both for student and staff. The authors have included some specific examples and those relating to biochemistry include a study of alkaline phosphatase in rat tissue (subcellular distribution of enzyme, kinetic characteristics, purification scheme, comparative studies, a study of D N A from eukaryotic and prokaryotic organisms (homogeneity of D N A , base compositions, melting profiles, denaturation/renaturation), and affinity chromatography of dehydrogenase enzymes (purification scheme, affinity ligands, co-purification of other enzymes, tissue specificity).
The authors describe an inexpensive method for studying molecular compressibility in proteins using flexible copper wire. They suggest that this kind of information is useful in considering the orientation of a protein in a biological membrane, the preferential orientation of a protein subunit in a molecular complex or the behaviour of enzymes under high hydrostatic pressure. The study involves constructing a wire model incorporating all the known features of molecular structure (disulphide bonds, a-helices, [3-structure, random coil) and subjecting this to a variety of stresses (variable weights attached to specific parts of the structure) and measuring the resultant displacements at various points on the structure. The model is sufficiently elastic to allow restoration of the original segment position upon removal of the stress. The application of the method is illustrated with a model of hen egg-white lysozyme which was analysed along three different axes from different orientations. From the results the authors observed a series of major and minor molecular displacements which correlated with certain secondary structure features. They go on to suggest that their results are significant and that the observed large compressibility along the axis between residues 84-110 may correspond to a widening and narrowing of the enzyme cleft which in turn could be responsible for the observed increase in enzymic activity under high hydrostatic pressure.
[Publications Despatch Unit, BTEC, Central House, Upper Woburn Place, London WC1H 0HH, UK]
Waiters, D E, Pearlstein, R A and Krimmel, C P A Procedure for
[Department of Biological Sciences, SUNY - - Albany, Albany, NY 12222, USA]
Preparing Models of Receptor Sites. J Chemical Education 63, 869-872 (1986)
Hudson, D How Important is Question Sequence? J Chemical Education 64, 11-12 (1987) As the author points out, it is generally held that sequencing multiple choice questions in order of increasing difficulty is beneficial in that it helps to reduce anxiety, improves morale and motivation, reduces the likelihood of non-completion of tests and provides a more reliable measure of ability. The evidence for this belief, however, is based more on judgement and hunch rather th~n empirical evidence. For this reason the author designed an experiment in which the effect on test statistics of varying the difficulty order of multiple choice items could be evaluated. One test contained fifty multiple choice questions arranged in three different difficulty orders (easy-to-hard, hardto-easy, and random) using facility values supplied by an examination board. The test forms were randomly distributed to 206 pupils as part of a mock 'O' level examination. A similar investigation was undertaken for 157 ' A ' level students. From the results it is clear that the easy-to-hard test increased the mean test score and the hard-to-easy lowered it, the differences being significant. More detailed analysis revealed that the improvements of test scores in easy-to-hard sequenced tests were greater for high ability than for low ability students. In comparing the reliability coefficients there were no significant differences between random and easy-to-hard sequenced tests.
BIOCHEMICAL
EDUCATION
15(3) 1987
A simple, straightforward and inexpensive procedure is described for constructing three-dimensional models of receptor sites using space-filling models of active compounds as templates. Two procedures are described, one using plastics such as Polyform (used in orthopaedic medicine) which are rigid at room temperature but maleable and flexible at 70°C and the other heavy-duty aluminium foil which is less expensive but produces models that are significantly more fragile. In the case of the heatpliable plastics a sheet is warmed in a water-bath for a few minutes and then shaped around a space-filling model. The material can be further modified by heating small regions in hot water or with a heat-gun and extra pieces can be added by heating and welding or with solvent-based glue. For aluminium foil, the authors suggest laminating several sheets with spray adhesive in order to increase the rigidity of the foil. In both cases it is possible to map possible binding sites such as hydrogen-bond donors and acceptors, ionic groups, charge-transfer sites and hydrophobic regions using markers or paint. The application of the technique is illustrated for a receptor site for aspartic acidbase sweeteners such as aspartame. Interesting and helpful observations can be made by using skeletal models with the receptor sites made from space-filling models. [Department of Medicinal Chemistry, Searle Research and Development, 4901 Searle Parkway, Skokie, Illinois 60077, USA]
Monitor CHARLES F A BRYCE
Department of Biological Sciences Napier College of Technology Edinburgh, Scotland
[Department of Education, University of Auckland, Auckland, New Zealand]
BTEC Projects in the Areas of Biochemistry and Chemistry.
Marfey, P and Klein, L Can We Learn Anything from Simple
BTEC Higher National Courses. Code No 09-031-6, pp 19 (1986)
63, 975-976 (1986)
Mechanical Models of Globular Proteins? J Chemical Education
This is a set of guidelines prepared by the Board for Science of the Business and Technical Education Council (BTEC) intended for project supervisors on BTEC Higher National Courses but it will certainly be of much wider use. Many of the points made are common sense but this does not detract from the text since there are many useful tips and all of the issues surrounding the design, implementation and assessment of student projects have been collected and distilled in a single brief document. The authors describe the characteristics of projects including staff and student responsibilities, the identification of suitable projects which should not have unrealistically high academic content, should not involve overly complex apparatus or techniques and which need not necessarily be original. A checklist is given of contributions expected of students, considered under nine headings. On assessment, the authors suggest that a distinction be made between the practical work and the project report per se and that further subdivision might also be helpful. The organisation of projects is discussed with practical suggestions which may help in the running of individual or group projects, both for student and staff. The authors have included some specific examples and those relating to biochemistry include a study of alkaline phosphatase in rat tissue (subcellular distribution of enzyme, kinetic characteristics, purification scheme, comparative studies, a study of D N A from eukaryotic and prokaryotic organisms (homogeneity of D N A , base compositions, melting profiles, denaturation/renaturation), and affinity chromatography of dehydrogenase enzymes (purification scheme, affinity ligands, co-purification of other enzymes, tissue specificity).
The authors describe an inexpensive method for studying molecular compressibility in proteins using flexible copper wire. They suggest that this kind of information is useful in considering the orientation of a protein in a biological membrane, the preferential orientation of a protein subunit in a molecular complex or the behaviour of enzymes under high hydrostatic pressure. The study involves constructing a wire model incorporating all the known features of molecular structure (disulphide bonds, a-helices, [3-structure, random coil) and subjecting this to a variety of stresses (variable weights attached to specific parts of the structure) and measuring the resultant displacements at various points on the structure. The model is sufficiently elastic to allow restoration of the original segment position upon removal of the stress. The application of the method is illustrated with a model of hen egg-white lysozyme which was analysed along three different axes from different orientations. From the results the authors observed a series of major and minor molecular displacements which correlated with certain secondary structure features. They go on to suggest that their results are significant and that the observed large compressibility along the axis between residues 84-110 may correspond to a widening and narrowing of the enzyme cleft which in turn could be responsible for the observed increase in enzymic activity under high hydrostatic pressure.
[Publications Despatch Unit, BTEC, Central House, Upper Woburn Place, London WC1H 0HH, UK]
Waiters, D E, Pearlstein, R A and Krimmel, C P A Procedure for
[Department of Biological Sciences, SUNY - - Albany, Albany, NY 12222, USA]
Preparing Models of Receptor Sites. J Chemical Education 63, 869-872 (1986)
Hudson, D How Important is Question Sequence? J Chemical Education 64, 11-12 (1987) As the author points out, it is generally held that sequencing multiple choice questions in order of increasing difficulty is beneficial in that it helps to reduce anxiety, improves morale and motivation, reduces the likelihood of non-completion of tests and provides a more reliable measure of ability. The evidence for this belief, however, is based more on judgement and hunch rather th~n empirical evidence. For this reason the author designed an experiment in which the effect on test statistics of varying the difficulty order of multiple choice items could be evaluated. One test contained fifty multiple choice questions arranged in three different difficulty orders (easy-to-hard, hardto-easy, and random) using facility values supplied by an examination board. The test forms were randomly distributed to 206 pupils as part of a mock 'O' level examination. A similar investigation was undertaken for 157 ' A ' level students. From the results it is clear that the easy-to-hard test increased the mean test score and the hard-to-easy lowered it, the differences being significant. More detailed analysis revealed that the improvements of test scores in easy-to-hard sequenced tests were greater for high ability than for low ability students. In comparing the reliability coefficients there were no significant differences between random and easy-to-hard sequenced tests.
BIOCHEMICAL
EDUCATION
15(3) 1987
A simple, straightforward and inexpensive procedure is described for constructing three-dimensional models of receptor sites using space-filling models of active compounds as templates. Two procedures are described, one using plastics such as Polyform (used in orthopaedic medicine) which are rigid at room temperature but maleable and flexible at 70°C and the other heavy-duty aluminium foil which is less expensive but produces models that are significantly more fragile. In the case of the heatpliable plastics a sheet is warmed in a water-bath for a few minutes and then shaped around a space-filling model. The material can be further modified by heating small regions in hot water or with a heat-gun and extra pieces can be added by heating and welding or with solvent-based glue. For aluminium foil, the authors suggest laminating several sheets with spray adhesive in order to increase the rigidity of the foil. In both cases it is possible to map possible binding sites such as hydrogen-bond donors and acceptors, ionic groups, charge-transfer sites and hydrophobic regions using markers or paint. The application of the technique is illustrated for a receptor site for aspartic acidbase sweeteners such as aspartame. Interesting and helpful observations can be made by using skeletal models with the receptor sites made from space-filling models. [Department of Medicinal Chemistry, Searle Research and Development, 4901 Searle Parkway, Skokie, Illinois 60077, USA]