On left and right:Symmetry and Chirality in Molecules and Design

David Avnir

Institute of ChemistryThe Hebrew University of Jerusalem

 

Shenkar, 23/12/2014

1. Why is a chemist visiting Shenkar’s design department?

Insulin

Haemoglobin

Quasi-crystals

Diffusion-reaction pattern

Symmetry - a universal language of shape and structure

Mirror symmetry

Rotational symmetry

Rotational and mirror symmetries combined

Our focus: Mirror symmetry

Called also reflection symmetry, bilateral symmetry

Why is this symmetry called “mirror symmetry”?

Combining an object with its mirror reflection produces that symmetry

Combining an object with its mirror reflection produces mirror symmetry

8

2D mirror symmetry in chemistry

3D molecular mirror symmetry

Zeolite

Carbon nanotube

Alexander McQueen(1969 – 2010)

2D-Mirror symmetry, textile: scarves design

Alexander McQueen

The basic 3D mirror symmetry in textile design for fashion

3D mirror symmetry of the body preserved in textile design

2. Moving away from mirror symmetry - chirality

Near symmetry in chemistry

cyclohexane

HIV Protease

Near-symmetry in McQueen’s design

Bjork

Far-away from mirror symmetry

Far-away from mirror symmetry – because of design

Far-away from mirror symmetry – because of body posture

Far-away from mirror symmetry – because of body posture and design

Chirality and handedness

When mirror symmetry is removed, a special property emerges :The object may come in two forms:

a left-form and a right-form (handedness)

*These left and right forms are called enantiomers

*Enantiomers are different objects ,but they look very similar .

The similarity is because they aremirror-images of each other

The difference is that theycannot coincide with each other.

If there is mirror symmetry, the object coincides with its mirror image, the object is achiral – and there is no pair of enantiomers

28

Chirality is an extremely important property in the natural sciences

Life is based on left-handed amino acids and right-handed sugars

Why is it so important?

To understand it let us take the case of spiral chirality

Diastereomeric (DS) interactions

The hand-glove interactions

The interaction between a right-hand (Rh) and a right-glove (Rg) is different from the interaction of a right-hand (Rh) with a left-glove (Lg)

Two different interactions :

Rh-Rg Rh-Lg

Comfortable vs. Very awkward

In the life-sciences chiral interactions are highly important

Reason: All biological receptors are chiral; therefore:

The interaction: Left-molecule receptorand the interaction: Right-molecule receptorare different

“How would you like to live in a Looking-glass House, Kitty? I wonder if they'd give you milk, there? Perhaps Looking-glass milk isn't good to drink“

“Through the Looking Glasss, and What Alice Found There”, Lewis Carrol (1871)

Left-handed and right-handed molecules:

*Taste differently

*Smell differently

*Can heal or kill (Thalidomide)

Carvone) R( :Spearmint (S): Caraway

)kummel (

3. Relevance of chirality considerations to design

Many textile design patterns are chiral

But now we know that such designs can come in left or right forms; here they are:

The enantiomeric pair of the same design

Why has McQueen selected the right spiral?

Is it an important question for design?

Our biological receptor at focus :The chiral brain

*The left and right hemispheres of the brain are very unequal

*Therefore, no mirror symmetry – the brain is chiral

*Specifically: the brain is a chiral information receptor

*Therefore, if the information – visual – is chiral, DS interactions result between the brain and the information Therefore, left and right

objects must be perceived differently by the brain

Psychology of aesthetic perception

“ When some pictures are mirror reversed, aesthetic evaluations of them change dramatically”.

“When a painting is viewed in a mirror… even the meaning can change”…

“The first major finding… was that paintings containing left-to-right directional cues were preferred ”…

A. M. Mead and J. P. McLaughlin, Brain and Cognition, 20, 300 (1992)

N. Konstom, “Rembrandt’s use of models and mirrors”, BurlingtonMagazine, 99, 94 (1977)

Rembrandt’s 2D-chiral preferences

Are chirality considerations relevant/important to textile design ?

First answer:

Yes, the left enantiomer and the right enantiomer of the same design may be perceived aesthetically in a different way.

4. Additional considerations in brief

Induction of chirality: Accessories

Induction of chirality by 3D texture

Alexander McQueen

Illumination induces chirality

Randomness is always a source of chirality

The specific label is not important :Handedness labeling is an agreed convention, not an

inherent property like chirality itself

Are these left- or right-handed?

Chirality has a degree

The environment strongly affects perception

Posture and design - The four possibilities:

# Left design – Left posture

# Left design – Right posture

# Right design – Left posture

# Right design – Right posture

Diastereomeric interactions with artificial chiral environments

Diastereomeric interactions with natural chiral environments

Conclusion

Are chirality considerations relevant to design?

First answer :Yes, the left enantiomer and the right enantiomer of the same design may be perceived aesthetically in a different way.

Second answer :

Yes - most environments are chiral, and therefore left- and right versions of the same design, interact with it differently.