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Negative stain electron micrographs of P2 virions (A), P2 procapsids from the CsCl top fraction (B), P4 virions (C) and P4 procapsids (top fraction, D). A few larger shells are visible in the procapsid fractions in B and D (white arrows). A GroEL particle is indicated in B (black arrowhead). Scale bar, 100 nm.
