Below is a list of stars arranged in order of decreasing luminosity (increasing bolometric magnitude). Accurate measurement of stellar luminosities is quite difficult in practice, even when the apparent magnitude is measured accurately, for four reasons:
LSS may refer to:
Lanosterol synthase is an oxidosqualene cyclase (OSC) enzyme that converts (S)-2,3-oxidosqualene to a protosterol cation and finally to lanosterol.Lanosterol is a key four-ringed intermediate in cholesterol biosynthesis. In humans, lanosterol synthase is encoded by the LSS gene.
In eukaryotes, lanosterol synthase is an integral monotopic protein associated with the cytosolic side of the endoplasmic reticulum. Some evidence suggests that the enzyme is a soluble, non-membrane bound protein in the few prokaryotes that produce it.
Due to the enzyme’s role in cholesterol biosynthesis, there is interest in lanosterol synthase inhibitors as potential cholesterol-reducing drugs, to complement existing statins.
Though some data on the mechanism has been obtained by the use of suicide inhibitors, mutagenesis studies, and homology modeling, it is still not fully understood how the enzyme catalyzes the formation of lanosterol.
Before the acquisition of the protein’s X-ray crystal structure, site-directed mutagenesis was used to determine residues key to the enzyme’s catalytic activity. It was determined that an aspartic acid residue (D455) and two histidine residues (H146 and H234) were essential to enzyme function. Corey et al. hypothesized that the aspartic acid acts by protonating the substrate’s epoxide ring, thus increasing its susceptibility to intramolecular attack by the nearest double bond, with H146 possibly intensifying the proton donor ability of the aspartic acid through hydrogen bonding. After acquisition of the X-ray crystal structure of the enzyme, the role of D455 as a proton donor to the substrate’s epoxide was confirmed, though it was found that D455 is more likely stabilized by hydrogen bonding from two cysteine residues (C456 and C533) than from the earlier suggested histidine.
close the door
i feel a breeze hold me please
i hate to be alone
it's a cold night,
turn off the light
come take my hand and...
CHORUS:
listen,
to these things i have to say
please understand, she
left me all alone again...
clear the room of every memory
i don't want our song back on
it's an endless maze
take away this haze
mend my heart and...
(repeat chorus 2x)
BRIDGE:
turn away, don't want you to see me cry
i just want things the way they were
why is it so hard to say goodbye?
wipe my tears and...
(repeat chorus)
so this i ask of you
please stay with me
until she comes back
until she comes
until she comes back
until she comes
please listen and stay
until she comes
until she comes back