With no explanation, label each line with "O", "other-biologything", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
Viral
entry
to
the
CD4+
cell
begins
with
attachment
of
the
R5
HIV-1
glycoprotein
120
(
gp120
)
to
the
CD4+
T-cell
receptor
,
which
produces
a
conformational
change
in
gp120
and
allows
it
to
bind
to
CCR5
,
thereby
triggering
glycoprotein
41
(
gp41
)
mediated
fusion
of
the
viral
envelope
with
the
cell
membrane
and
the
nucleocapsid
enters
the
host
cell
(
Figure
1
)
.
Viral:O
entry:O
to:O
the:O
CD4+:other-biologything
cell:O
begins:O
with:O
attachment:O
of:O
the:O
R5:other-biologything
HIV-1:other-biologything
glycoprotein:other-biologything
120:other-biologything
(:O
gp120:other-biologything
):O
to:O
the:O
CD4+:other-biologything
T-cell:other-biologything
receptor:other-biologything
,:O
which:O
produces:O
a:O
conformational:O
change:O
in:O
gp120:other-biologything
and:O
allows:O
it:O
to:O
bind:O
to:O
CCR5:other-biologything
,:O
thereby:O
triggering:O
glycoprotein:other-biologything
41:other-biologything
(:O
gp41:other-biologything
):O
mediated:O
fusion:O
of:O
the:O
viral:O
envelope:O
with:O
the:O
cell:O
membrane:O
and:O
the:O
nucleocapsid:O
enters:O
the:O
host:O
cell:O
(:O
Figure:O
1:O
):O
.:O