Chapter Text
“...and of course it refers to the property of asymmetry in certain molecules. It stems from the Greek word “cheir”, meaning hand – and rightly so. For chirality is often described in terms of left and right. Just as our hands are mirror images of each other,” Sherlock says, taking John’s hand in his own, comparing the size between them. “But cannot be superimposed – chiral objects possess that similar characteristic.”
“I see,” Watson mumbles, eyes closed.
Sherlock has been rambling for some forty minutes now – and while Watson has yet to fall asleep, he’s slipping slowly, his attention and replies growing more infrequent. It’s been longer, this time around. Then again, they went to bed earlier.
It’s – begun to be something Sherlock looks forward to. Being allowed to talk about his interests for hours on end, and it being a comfort to someone else, rather than a bother. It being a comfort to John, of all people.
“Go on,” Watson says, shuffling closer, and a warmth floods Sherlock’s chest.
Good god. The things he wouldn’t do for John Watson. “Right. Yes. Well, naturally, molecules can exhibit chirality when they possess a central carbon atom bonded to four different groups or atoms – known as the chiral center. The resulting molecule exists in two distinct forms – enantiomers.”
Watson’s face scrunches against Sherlock’s side. He doesn't open his eyes. “Enano-what's?”
“Enantiomers. Imagine a pair of gloves. They may appear identical at first glance, but upon closer inspection, you’ll find they, in fact, are rather mirror images of each other. Enantiomers are much like these gloves – they have the same chemical formula, but their spatial arrangement differs, leading to distinct properties.”
“Such as?”
“Mmm – well, they exhibit different effects on biological systems. A classic example can be found in the drug ibuprofen. It exists as a mixture of two enantiomers: S-ibuprofen and R-ibuprofen,” Sherlock goes on, as he tucks Watson’s hair behind his ear, moving it out of his face. “The S-enantiomer is responsible for the desired anti-inflammatory effect, while the R-enantiomer is less active. And so, by isolating and thus utilizing the active enantiomer, pharmaceutical companies can optimize the therapeutic efficacy of the drug while minimizing its side effects.”
“Mmm. I see,” John breathes. His eyes are open now, and he peers up at Sherlock in the dark. “The left and right hands metaphor makes a bit more sense now, anyway.”
“Yes – it’s quite often used, based on their asymmetry-” Sherlock’s voice trails off.
John has sat up, some, scooted up until his face is near-level with Sherlock’s. He’s looking very attentively, even in the darkness, searching Sherlock’s face. His breath is minty.
Sherlock blinks.
There’s a moment of silence. There’s a nervousness, an anticipation, and Sherlock’s stomach flips upon his deduction of its cause.
“Can I – can we kiss? Can I kiss you?” John murmurs.
“Yes,” Sherlock returns, even as his hand slips back against John’s neck, up, meeting the shorter sides of his hair, the ends of curls. “Do, immediately.”
And John’s sitting up, scooting forward on his knees, twisting to fit against Sherlock’s chest, and Sherlock’s hand follows along. John’s eyes are closed when he leans forward, but Sherlock keeps his open - and then John’s lips are against his, and it’s a connection, a togetherness that’s as fulfilling as it is unmistakable.
He takes it in, all of it, the way John’s eyebrows rise a fraction at the contact, the way his breath hitches in his throat, how his heart beats quicker in his chest, pounds heavily against Sherlock’s. It only lasts a moment, then he’s pulling away, sinking down into Sherlock’s arms again.
They settle.
Sherlock shifts.
And John is smiling against Sherlock’s chest, ears flushed and warm even as his heart rate begins to steady.
So Sherlock goes on. “Then there are biological molecules – such as amino acids and sugars – which are predominantly chiral. All naturally occurring amino acids in proteins are of the…”