Reading Comprehension

PT155 · S3 · P3 · Q16 Nanoscale Computer Chips

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This passage was adapted from an article published in 2000.

Topic

Belcher and Hu's research using peptides — short amino-acid chains — to build nanoscale electronic components.

Framework

Highlight Noteworthy. The author isn't arguing against anyone; the author is showcasing a promising approach to a coming problem in chip miniaturization.

Main Point

Conventional miniaturization is about to hit a hard physical limit, and Belcher and Hu's peptide-based approach is a promising route to building electronics below that limit. They have already identified hundreds of peptides that bind to specific semiconductor crystals and are now designing peptides that can act as molecular "glue" — exactly the kind of finesse needed for self-assembling nanocircuits.

P1: Why this work matters

The race to make computer chips smaller is approaching a wall (~2010): current transistors can't go below 25 nanometers. Living cells, however, routinely build complex structures at smaller scales. So researchers want to harness biological molecules. Most work focuses on DNA — Belcher and Hu are pursuing peptides instead.

P2: How they got there

The idea grew out of Belcher's discovery that a specific peptide directs calcium-carbonate crystallization in abalone shells. She and Hu reasoned that peptides able to direct crystal growth in semiconductor materials could be a tool for building nanoscale electronics. Since no known peptide had this property, they screened a billion random peptides against three semiconductor materials and isolated ones that bound to specific faces of specific crystals — then refined them via accelerated-evolution-style methods.

P3: Where things stand and what's next

To assemble a real toolkit, many more binding peptides are needed. They're making progress: hundreds of crystal-manipulating peptides across 20+ semiconductor materials, plus newly designed peptides that bind to two different crystals at once — molecular glue. That kind of nanoscale finesse is what self-assembling circuits will require.

16.

Which one of the following most accurately expresses the main point of the passage?

  1. Although preliminary results suggest that

    Too Pessimistic

    The ending of this answer, "enough obstacles remain to make such an outcome unlikely" is overly pessimistic. Our author mainly stayed out of this passage. His only evaluative comment in the final paragraph is optimistic: "they are making progress on that quest". This answer does what many choice (A)'s do -- it over-values the last thing you read.

    1% picked this

  2. Advances in computer chip speed

    Wrong Emphasis

    This answer seems pretty darn acceptable. Its weakest part is treating Belcher and Hu as just an example among "various current research projects". True, there is also work going on to see if we can harness DNA for the sake of advancing computer chip speed/efficiency, but only half a sentence in the passage is allocated to that. The 2nd and 3rd paragraph are specifically about B&H's peptide research, so the emphasis of this main clause just seems to unfairly leave them on the side of the road: Advances in chip speed may depend on the outcome of various current research projects.

    28% picked this

  3. Correct

    Belcher and Hu’s research on

    Why this is right

    Unlike (B), this answer correctly makes B&H's research the subject of the main clause, since it was the focus of the passage. The strength of "might eventually be applied" is correct given the early, tentative, but encouraging state of this field. And the answer choice relates their research back to the context of the first paragraph: solving the size limit problem of conventional transistors.

    Skill tested: Main Point · how this choice captures the passage's function is the move to repeat next time.

    68% picked this

  4. Belcher and Hu’s discovery of

    Wrong Takeaway

    The first half of this sentence is okay, but the second half goes off the rails. The author wouldn't tentatively say that semiconductor materials might bind to biological compounds. At the end of the 2nd paragraph, "they found a few peptides that .. bound .. to one of the [semiconductor] crystals in the experiment". We already know now that we can get certain peptides to bind with certain semiconductor materials. We might be able to use this knowledge to build super tiny organic circuits.

    3% picked this

  5. The application of Belcher’s work

    Wrong Big Picture

    The reason we're talking about Belcher's work is not to make a broad point about how pure science can have surprising practical benefits. Our big picture is Problem / Solution ... we're talking about Belcher's work because it might be the Solution to the Problem of hitting the minimum size threshold for transistors.

    0% picked this

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