This passage was adapted from an article published in 2000.
Competition to make computer chips smaller and,
consequently, faster and more efficient has driven a
technological revolution, fueled economic growth, and
rapidly made successive generations of computers
(5) obsolete. Yet at the current rate of progress this march
toward miniaturization will hit a wall by about 2010—
for many, an unthinkable prospect. The laws of physics
dictate that, with current methods, properly functioning
transistors—the electronic devices that make up
(10) computer chips—cannot be made smaller than 25
nanometers (billionths of a meter). In living cells,
however, natural chemical processes efficiently and
precisely produce extremely complex structures below
this size limit, so there may be hope of using some such
(15) processes to yield tiny molecules that can either
function like transistors or be induced to combine with
other materials in carefully controlled ways to construct
whole nanocircuits. Much current research is aimed at
harnessing DNA to this end, but materials chemist
(20) Angela Belcher and physicist Evelyn Hu are
investigating a different molecular pattern maker:
peptides, amino acid chains that are shorter than
proteins.
The project grew out of Belcher’s doctoral
(25) research on abalone. Her research group discovered in
the mid-1990s that a specific peptide causes calcium
carbonate to crystallize into the structure found only in
the tough abalone shell. From that discovery, Belcher
and Hu, Belcher’s postdoctoral adviser at the time,
(30) realized that if they found peptides able to direct the
crystal growth of the semiconductor materials that
form transistors, they might have a tool for building
nanoscale electronics. However, no known peptide was
able to bind to semiconductor materials to cause the
(35) development of particular crystalline structures as
some peptides did with calcium carbonate. So Belcher,
Hu, and their colleagues grew a random assortment of one
billion different peptides and tested whether any of
them bound to silicon, gallium arsenide, or indium
(40) phosphide crystals—three widely used semiconductor
materials. They found a few peptides that not only
bound exclusively to one of the crystals in the
experiment but also latched onto a particular face of the
crystal. Through a process resembling accelerated
(45) evolution, they developed additional related
peptides from those that had the initially promising
characteristics.
Hu says that in order to use such a method to
assemble a set of circuit-building tools it would be
(50) necessary to identify many additional organic
compounds that bind to circuit-component materials.
The group is making progress on that quest. As they ,
have expanded their targets to 20 more semiconductor
materials, their cache of crystal-manipulating peptides
(55) has ballooned into the hundreds. They are also
designing new peptides that bind to two different
crystals at once, acting as a daub of glue. It will take
that kind of finesse at the nanoscale to produce self
assembling circuits.
1. Which one of the following most accurately expresses the main point of the passage?(A) Although preliminary results suggest that Belcher and Hu's research on peptides and semiconductors could result in a breakthrough in the miniaturization of computer chips, enough obstacles remain to make such an outcome unlikely.
(B) Advances in computer chip speed and efficiency beyond the year 2010 may depend on the outcome of various current research projects, including that conducted by Belcher and Hu, which focus on using peptides to bind different crystals together.
(C) Belcher and Hu's research on the abilities of some peptides to bind to semiconductor materials indicates that peptides might eventually be applied to the production of computer chips with transistors smaller than the lower limit set by current methods.
(D) Belcher and Hu's discovery of peptides that cause the development of a particular crystalline structure in a natural biological context suggests that semiconductor materials might bind to biological compounds.
(E) The application of Belcher's work on abalone to the world of semiconductors shows that pure scientific research can have unexpected practical repercussions.
2. The words "that kind of finesse" (final sentence of the passage) refer primarily to(A) the ability to translate abstract, theoretical concepts in computer design into concrete applications
(B) the creativity that was necessary to apply knowledge gained from DNA research to molecular pattern makers other than DNA the development of sophisticated methods of
(C) observing the behavior of crystalline structures that are both extremely tiny and extremely complex
(D) the ability to differentiate peptides that interact chemically with at least one semiconductor material from very similar peptides that do not interact with any such materials
(E) the ability of researchers to manipulate organic compounds in ways that satisfy very specific circuit-construction needs
3. Which one of the following statements about the peptides that Belcher and Hu tested in relation to semiconductors can be most reasonably inferred from the passage?(A) At least some of them did not previously exist in nature.
(B) At least one of them was found to bind to three different semiconductor compounds.
(C) At least some of them were tested in relation to silicon but not in relation to gallium arsenide.
(D) At least one of them was in use in. the computer chip industry prior to Belcher and Hu's research.
(E) Other researchers had previously tested at least some of them for possible reactions with semiconductor materials other than silicon,. gallium arsenide, and indium phosphide.
4. Which one of the following situations involving volatile oils is most analogous to the situation involving peptides that is presented in the passage?(A) A group of researchers, whose experimentation has focused on the chemical properties of certain synthetic volatile oils, abandons that line of inquiry on receiving a grant to study whether certain species of trees contain acids that could have antiviral properties in human medical applications.
(B) A group of researchers extracts several volatile oils from the leaves of certain species of trees and, while testing each of the oils to determine whether it has antifungal properties that could make it useful in human medical applications, they discover that one of the oils is a powerful insecticide.
(C) A group of researchers synthesizes several volatile oils that, when combined, are found to be useful as a fungicide on fruit trees. Through further experimentation, they find that this same combination of oils has antiviral properties in human medical applications.
(D) A group of researchers observes that a volatile oil contained in an antifungal product used on fruit trees can cause mutations in the trees. As a result, they launch a research project to determine whether similar oils that are used in human medical applications might cause genetic damage.
(E) A group of researchers, noting that a volatile oil secreted by a certain species of tree protects it from a type of fungal infection, synthesizes several similar oils and tests them for possible antibacterial activity that might make them useful in human medical applications.
5. The primary role of the first two sentence We passage is to help the reader understand(A) why research of the sort done by Belcher and Hu was not previously undertaken by other researchers
(B) the purpose and importance of the research that Belcher and Hu have undertaken
(C) the skepticism with which some members of the scientific community have greeted Belcher and Hu's research
(D) a commonly held viewpoint against which Belcher and Hu's research is directed
(E) a hypothesis that Belcher and Hu's research is designed to test
6. The passage most strongly supports which one of the following?(A) Some peptides that bind to gallium arsenide also bind to indium phosphide.
(B) Researchers besides Belcher and Hu and their colleagues have studied the possibility of using peptides in the assembly of nanocircuits.
(C) Neither Belcher nor Hu has done major scientific research on organic compounds other than peptides.
(D) Silicon, gallium arsenide, and indium phosphide are not the only semiconductor materials to which peptides have been found to bind.
(E) Peptides have been used in industrial applications that are not related to semiconductors.
7. Which one of the following, if true, lends the most support to a prediction of an eventual commercial application of Belcher and Hu's research into peptides and semiconductors?(A) Belcher and Hu's early successes in synthesizing peptides that bind to semiconductors have sparked renewed interest in possible DNA applications in the construction of nanocircuits.
(B) For almost any semiconductor material that is used in a computer circuit, there are many other semiconductor materials that function in the same way and could be substituted for it.
(C) The number of peptides that bind to two different crystals at once appears to be smaller than the number of peptides that, although they bind to two different crystals, cannot bind to both at the same time.
(D) The one billion peptides that Belcher and Hu grew and tested in the initial stages of their research was nearly four times the number of peptides they grew and tested subsequently.
(E) Expectations of continuing high costs of synthesizing the peptides that Belcher and Hu have found to bind to semiconductors have tended to restrict the number of scientists contemplating possible research into peptide uses in nanocircuits.