This contest is an attempt to promote scientific knowledge among community in a fun and interesting way with the help of molecules.
Some people like to travel around the world and tell others stories about what happens outside of our organisms/cells in other countries.
And with “Identify the molecule” contest you can try to travel inside our own organism/cells and cells of the organisms around us.

For more information about this contest read "Identify the molecule" contest. Upgrade (the league, additional bonuses and more) post.

Prizes/bonuses:

The prize here is

1. knowledge

facts, information, and skills acquired through experience or education; the theoretical or practical understanding of a subject
[Oxford Dictionary of English, 3rd Edition, Oxford University Press, 2010]

That understanding of our own organism and organisms around us is the real prize in the case of this contest. No matter what happens (whether or not you get 100 STEM), you can win (can acquire the knowledge by investigating different sources of information, remembering and using it to your advantage in the future).

2. 100 STEM

STEMGeeks is a community focused on STEM topics rewarding engagement with STEM tokens. STEMGeeks is powered by the Steem blockchain with it's own distribution model for STEM tokens in addition to the potential STEEM tokens.
STEM stands for Science, Technology, Engineering, Math and includes a wide range of science and technology topics.
[source]

3. 200 TMN

Aside from STEM I’d like to add TMN tokens.
For the uninitiated, TMN is the token of TranslateMe project (it’s about combining blockchain technology (NEO in this case) with translation industry).
The reason I’m going to add this token for the prize pool of this contest is not only because I have them, but because this contest is quite scientific, and TranslateMe project might help to solve the “lost” science problem.
For more on this you can read my post regarding TranslateMe (TranslateMe (or Decentralization meets Translation industry). Part 2. The “missing puzzle piece” of scientific ecosystem. General overview) (and other posts of that series).

For more information on crypto-bonuses for this league, please refer to "Identify the molecule" contest. Upgrade (the league, additional bonuses and more) post.

Consider these tokens as a bonus.

Images and text are the clues for you to guess a riddle (the name of the molecule in this case).

Note that

a) even though this contest is called “Identify the molecule”,
-> molecule (singular)
sometimes it’s not just a molecule which is responsible for a specific function, but rather a complex of molecules.
Example:
cytochrome c oxidase (Complex IV)

is a large transmembrane protein complex… It is the last enzyme in the respiratory electron transport chain of cells located in the membrane.
source

b) some molecules/complexes have different names. For example, other names for cytochrome c oxidase (example above) are

Complex IV (mitochondrial electron transport).
Cytochrome a3.
Cytochrome aa3.
Cytochrome oxidase.
Warburg's respiratory enzyme.
source

Any of those names would be a valid entry.

c) Some almost identical molecules are grouped into classes / groups / families.
Example:
Helicases are divided into 6 groups. RecD and Dda molecules belong to helicases group (Superfamily 1 (SF1)). In this case you would need to guess only the name of the group –> Helicase/ Helicases.

d) Some proteins can have different forms – isoforms.
Example:
There’re trypsin 1 and trypsin 2. In this case you would need to guess only the general name – trypsin.

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Important

In order to get TMN, you’ll need to have NEO-wallet and provide me your public NEO-address.
If you don’t have it yet, don’t worry, I published a post on how/where to get it (O3 wallet).
Note that NEO-addresses provided by exchanges will not work in this case (+ it's safer NOT to keep your funds on exchanges). It's highly recommended to get O3 wallet.

If there’re no winners on any stage, the prize will be distributed equally among all users who provided any guesses for molecules.

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Riddle

This molecule is one of the main reasons of the fact that the more you eat, the less you want to do that (unless there’re some serious issues (especially genetic) with your health).
On the other hand, the molecule is a part of the system that makes us hungry when we need food [1].

(Cartoon representation. The image was created by me with the help of PyMol - open source tool for molecular visualization/exploration. PDB-file was obtained from PDB)

Its primary function is to serve as a satiety factor/regulation of energy homeostasis, but it also demonstrates some other activities [2].
It takes part in the regulation of immune and inflammatory responses, bone formation, reproduction, etc [3].
It belongs to cytokine family of molecules and resembles IL-6 [4].

(Cartoon representation. The image was created by me with the help of PyMol - open source tool for molecular visualization/exploration. PDB-file was obtained from PDB)

The molecule circulates in blood in free and bound (to proteins) forms [4].

"Edited"

(Surface representation. The image was created by me with the help of PyMol - open source tool for molecular visualization/exploration. PDB-file was obtained from PDB)

Here’s the data showing where (in what human normal tissues) the gene of this molecule is expressed the most:

(in other words, those are the places where the molecule is present in abundance)

And here’s the data showing where (in what human normal tissues) the gene of this molecule is expressed the least:

(in other words, those are the places where the amount of this molecule is the lowest)

"Edited"

The molecule is one of the “characters” of ”The Hungry Gene” book.

The molecule’s name originates from the Greek word “leptos” (thin) [4].

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Rules

This contest lasts for 6 days.

Leave your guess (1 guess only) in the comments section of the post.

Don’t edit your comment and don’t provide any evidence that your answer is correct.

I’ll provide the answer in the comments section of the next post on the 7th day of the week’s stage.

The first user with correct answer is the winner.

Some of the clues have already been provided in the post.

Additional clues will be given in 2 days (on Monday, January 20, 2019, 20:00 ± 2 minutes UTC) (I’ll update this post).

And the rest of the clues will be provided in 2 more days (on Wednesday, January 22, 2019, 20:00 ± 2 minutes UTC) (I’ll update this post).

The reason is that some people might need less information to make conclusions that the others.

Additional clues will be added at the end of the "Riddle" section before the "Rules" section with "Edited" label.

The winner will be announced on Friday, January 24, 2019, 20:00 ± 2 minutes UTC in the comments section of the next post. Plus I’ll publish a detailed review of the riddle after a while.

I’ll transfer the tokens (STEM + TMN) (if the winner provides me his/her NEO-address) to the winner on that day (January 10) and add the transaction ID in the comments section.

I’m planning to run this contest every week.
So, you should expect to see the 2nd week’s riddle for January on Saturday, January 25, 2019, 20:00 ± 2 minutes UTC.

References

I’ll add all the references for this post later, because most of them contain the name of the molecule.
That would be a spoiler.
I’ll add them after a while.

"Edited"

1. Leptin. Molecule of the Month

2. Faggioni, R & Feingold, K & Grunfeld, C. (2002). Leptin regulation of the immune response and the immunodeficiency of malnutrition. FASEB journal : official publication of the Federation of American Societies for Experimental Biology. 15. 2565-71. 10.1096/fj.01-0431rev.

3. LEP leptin Homo sapiens (human)

4. https://en.wikipedia.org/wiki/Leptin

Important

This contest is the work in progress.
A lot can be changed in the future.
Any recommendations/suggestions are very welcome.
If you have any questions, feel free to ask them in the comments section.

All images (without the license specified) are used under the doctrine known in USA as "Fair Use" (similar doctrines are used in other countries). For more information visit the US Gov website