Scene of action:
A man with severe gastroenteritis, jaundice, decreased blood pressure and cardiovascular abnormalities wanted to see the Australian police in spite of being sick. He told that he was tried to get murdered and was stabbed by an umbrella in his leg when he was waiting for a tram in Melbourne. The chemists of ASIO determined that there is white substance which appears like a small metal pellet. So being a protein chemist and computational biologist I have to I identify the cause of his death and find out the protein responsible for his death.
The two polypeptide sequences are,
Blast: It compares amino acid sequences of different proteins or nucleotides of DNA sequences. BLAST compares the query sequence with the database in the library and it identifies the matching between them.
Score: It's quantitative estimate of the similarity of aligned protein sequence or segment of sequence. Scoring matrixes namely BLOSUM62, BLAST calculates the number or residues that are,
Identical: all identical residues are given a positive score.
Substituted: all residues substituted with similar residue are given positive score and all residues substituted with dissimilar residue are given a negative score.
Inserted or Deleted: all inserted or deleted residues are given a negative score.
E-value (expect value): It's the likelihood that an alignment with the same score or higher could be due to chance. Highly significant e values are very close to zero.
The BLAST results as follows:
Ricin a:
Ricin b:
Ricin:
Ricin is a cytotoxin produced by Ricinus communis seeds. It's a dimeric protein stored in the developing endosperm. The toxin composed of two chains namely
These two chains are connected by a disulfide bond. Each chain was N-gltcosylated and molecular mass of them were 32 kDa and 34 kDa respectively. RTB binds to the receptors on the surface of target cells and RTA which is having enzymatic activity attacks and inactivates ribosomes.
Details about Chain A and Chain B:
Chain A:
It is an n-glycoside hydrolase. It is composed of 267 amino acids. It is having both alpha helices and beta helices in it. It has three structural domains.
Reference:
Chain B:
It is a lectin. It is composed of 262 amino acids and that is able to bind terminal galactose on cell surface. It is bi-lobal and contains alpha and beta helices. It has three domains which help in the appearance of the RTB character.
Reference:
Bio warfare agent:
Ricin was used as toxic dust or coating for bullets and shrapnel during the First World War. During Second World War USA and Canada made their studies on ricin cluster bombs for a mass destruction. Thus ricin became one of the chemical weapons of USA with symbol given as WA.
Ricin is extremely toxic and used as chemical/biological warfare agent, which was rated as schedule 1 controlled substance. It's very powerful when compared to botulinum and anthrax. Another prospective thing is it's easy to produce when compared to botulinum and anthrax. There is no need of any care in growing castor plants and no need of asking permission, because its normal ornamental plant. In 1991 Al-Qaeda made an experiment on ricin which shows the non complexity in production of ricin. Worst side is there is no specific antidote for ricin.
Umbrella story: A Bulgarian secret police assassinated Georgi Markov in London Street. He shot him with a modified umbrella using compressed gas to fire a tiny pellet of ricin into his leg. After two days he died. When the doctors done autopsy they find a tiny pellet in his leg and they concluded the case as completely well planned murder.
References:
Conclusion:
After complete screening of the two polypeptide sequence we found that it was Ricin (sub units A & B).As said before ricin is a very poisonous substance and easy to produce it, not like as anthrax or tetanus. Even now it's being used as bioweapons.
The same kind of incident happened in 1978 in Bulgaria. Ricin was used as poisoning agent to kill that person.
In 2003 ricin was sent in a mail to white house after the 2001 anthrax attacks. But fortunately no fatality was recorded.
From this I conclude that that exact motto was to kill the Eastern European dissident without any clue left behind. So it's better to start investigating about the case considering as well pre planned assassination.
