Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lipid ion channels and the role of proteins   Synthetic lipid membranes in the absence of proteins can display quantized
conduction events for ions that are virtually indistinguishable from those of
protein channel. By indistinguishable we mean that one cannot decide based on
the current trace alone whether conductance events originate from a membrane,
which does or does not contain channel proteins. Additional evidence is
required to distinguish between the two cases, and it is not always certain
that such evidence can be provided. The phenomenological similarities are
striking and span a wide range of phenomena: The typical conductances are of
equal order and both lifetime distributions and current histograms are similar.
One finds conduction bursts, flickering, and multistep-conductance. Lipid
channels can be gated by voltage, and can be blocked by drugs. They respond to
changes in lateral membrane tension and temperature. Thus, they behave like
voltage-gated, temperature-gated and mechano-sensitive protein channels, or
like receptors. Lipid channels are remarkably under-appreciated. However, the
similarity between lipid and protein channels poses an eminent problem for the
interpretation of protein channel data. For instance, the Hodgkin-Huxley theory
for nerve pulse conduction requires a selective mechanism for the conduction of
sodium and potassium ions. To this end, the lipid membrane must act both as a
capacitor and as an insulator. Non-selective ion conductance by mechanisms
other than the gated protein-channels challenges the proposed mechanism for
pulse propagation. ... Some important questions arise: Are lipid and protein
channels similar due a common mechanism, or are these similarities fortuitous?
Is it possible that both phenomena are different aspects of the same
phenomenon? Are lipid and protein channels different at all? ... (abbreviated)

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The categories of this paper are: chem-ph
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: q-fin
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The categories of this paper are: cmp-lg