Reading Comprehension

PT155 · S3 · P3 · Q20 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.

20.

The primary role of the first two sentences of the passage is to help the reader understand

  1. why research of the sort

    Out of Scope

    Telling us that a Problem exists would be a way to explain why lots of research is being done in this area. It doesn't make sense to say that, "Because X is a looming problem, that's why researchers haven't undertaken to do research on X."

    2% picked this

  2. Correct

    the purpose and importance of

    Why this is right

    This is connecting Problem to Solution. The first two sentences lay out the Problem (we want smaller computer chips but have hit our limit) and Belcher and Hu's research is important because it could be used for the purpose of making computer chips even smaller than our current limit.

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

    88% picked this

  3. the skepticism with which some

    Unsupported

    The passage never mentions skepticism toward Belcher and Hu's research, and the first two sentences certainly don't express any. They're just describing an obstacle for the computer chip industry.

    2% picked this

  4. a commonly held viewpoint against

    Wrong View

    This answer accuses Belcher and Hu's research as being directed against the first two sentences, but it's directed toward solving the problem described in the first two sentences. The only commonly held viewpoint (if we can call it that) is, "It's unthinkable for us to have finally hit the limit of making computer chips smaller! I mean, there's got to be some way to get them even smaller, right?" Belcher and Hu are aligned with that view, because they're pursuing a way to get them even smaller.

    6% picked this

  5. a hypothesis that Belcher and

    Wrong Purpose

    The closest thing in the first two sentences to a hypothesis would be the prediction that "by 2010, we'll hit a wall where we can't make computer chips any smaller". 98% of the time we see hypothesis on LSAT, it means "a causal explanation" or "a scientific guess". But sometimes it just means the everyday sense of hypothesis which is "a guess". Kid 1: What do you think Dad's making for dinner tonight? Kid 2: My hypothesis is spaghetti. You can't really test that kind of hypothesis. You find out later whether you were right (seeing that water is boiling or that there is a box of spaghetti in pantry aligns with that hypothesis but it wouldn't count as testing it). Similarly, the guess that we'll hit a wall by 2010 isn't something you can test. It's a prediction. We'll find out when we get there whether it was true. Belcher and Hu's research wasn't designed to test that hypothesis. P2 explains that the research grew out of doctoral research on abalone.

    3% picked this

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