BetaCrustacyanin

1

• Beta-Crustacyanin
• The coloration of Lobster Shell
• Biological Medical Physics
• Kim, Indeog

2
Lobster mystery
INTRODUCTION
The crustacean of a live lobster is normally
dark blue.
When cooked, shell changes color from blue to red.
3
Astaxanthin (AXT)
INTRODUCTION

• AXT, the pigment molecule of lobster shell,
  reflects red color observing any other colors.
• Therefore, it looks red.
• It has been a mystery that even with AXT,
  lobster looks dark blue as long as its not
  exited by heat.
• Its due to the structure of a protein called
• beta-crustacyanin (ß-CR).
• Recently, a research revealed the molecular
  mechanism underlying this phenomenon.

4
Contents

• The molecular basis of the coloration mechanism

• The role of ß-CR
• Coloration Mechanism

• The finding process (Chemical/ Physical
  significance)

• The structure of Crustacyanin
• The Crystallization ß-CR
• X-ray Crystallography

• Findings

• Chemical Structure of AXT
• Characteristic of AXT in Color
• Coloration of alpha-crustacyanin

• Medical spin-offs

5
The role of ß-CR
MOLECULAR BASIS

• The key is ß-CR, the lobster shell protein.
• AXT (the pigment molecule) on its own is
  reddish.
• In living lobsters, AXTs are bound to ß-CR.
• ß-CR is able to change its shape, bending the
  shape of AXT molecule.
• Cooking the lobster, the ß-CR frees AXT setting
  the shell reddish.

6
Coloration Mechanism
MOLECULAR BASIS
AXT
AXT ß-CR
The crustacean of a live lobster (AXT ß-CR )
On cooking, AXT is separated from ß-CR
7
The structure of Crustacyanin
THE FINDIND PROCESS

• Zagalsky of Londons Royal Holloway College has
  established crustacyanins building blocks.
• Lobsters blue color originates from
  crustacyanins proteins holding the pigment
  molecules.
• Alpha-crustacyanin, the macromolecule coloring
  lobster shell is made up of eight ß-CR subunits.
• These subunits (ß-CR) consist of two smaller
  protein components (apoproteins) along with two
  AXT molecules.

8
The Crystallization of ß-CR
THE FINDIND PROCESS

• It was clear that lobsters blue color
  originates from Crustacyanins proteins (ß-CR)
  holding the pigment molecules (AXT).
• Having chemical components of
  alpha-crustacyanin, Zagalsky needed to determine
  their structure.
• Uncovering the structural basis of this
  interaction was tough. The crystallization of the
  massive crustacyanin macromolecule was very
  difficult.

9
X-ray Crystallography
THE FINDIND PROCESS

• To analyze the ß-CR complexs three-dimensional
  structure the research team used x-ray
  crystallography.
• The technique requires crystals of ß-CR.
• However, classic methods failed to produce the
  crystal.
• But, Imperial Colleges Naomi Chayen eventually
  cultivated the crystals using Microbatch
  method, in which the crystals were grown in oil.
• Finally, she could determine the structure of
  the ß-CR.

10
Chemical Structure of AXT
FINDINGS
The chemical scheme of the AXT
Three dimensional scheme of AXT
11
Characteristic of AXT in Color
FINDINGS
AXT changing color as the head groups rotate.
12
Coloration of alpha-crustacyanin
FINDINGS
Coloration of AXT (AXT floating into out of
CR )
AXT bound with ß-CR
13
The next step is to utilize this knowledge
MEDICAL SPIN OFF

• This discovery could lead to new treatments for
  a number of human diseases including cancer.
• AXT is a powerful antioxidant which protects
  cell membranes and tissues from damage
• - But AXT is chemically unstable and insoluble
  in water
• - Wrapping up this pigment (AXT) in a protein
  cage (CR) can provide a way to deliver its
  properties more effectively
• It can provide a more natural alternative to
  existing food colorants

14
THANK YOU