x ray crystallography

Human DNA: A history

DNA is an important part of modern crime evidence, but it is important to know when DNA is actually used in history, and the experiments it took to actually get DNA to be the robust science it is today. Hopefully this is helpful for your writing needs!

DNA Timeline

1866 – Gregor Mendel determines the principles of genetic inheritance

1902 – Sir Archibald Edward Garrod associated Mendel’s theories with human disease alkaptonuria (black urine or black bone disease, genetic disorder where the body cannot process the amino acids phenylalanine and tyrosine)

1944 – Oswald Avery, working with MacLeod and McCarty determines DNA as the “transforming principle”, while working with Streptococcus pneumoniae (bacteria causing pneumonia), it was determined that dead/heat-killed S-strain (which is lethal) can “transform” living R-strain (which is non-lethal) into lethal bacteria

1950 - Chargaff’s rules was developed by Edwin Chargaff, it basically states that there is a 1:1 ratio of pyrimidine and purine bases, that adenine = thymine, and guanine = cytosine, an important rule for base pairings and the DNA double helix structure

1952 – Alfred Hershey and Martha Chase experimented with T2 phage and elemental isotopes; phosphorus-32 labelled DNA while sulfur-35 labelled the proteins; the progeny infected unlabelled bacteria, and since phosphorus-32 showed up, it confirmed that DNA is the genetic material

1952 – Rosalind Franklin uses X-ray crystallography to photograph DNA fibres

1953 – James Watson and Francis Crick uses Franklin’s crystallography and previous research material to determine the double helix structure of DNA

1959 – an extra chromosome 21 is linked to Down’s syndrome

1965 – Marshall Nirenberg worked with E.coli bacteria cells to determine how DNA is involved with RNA and protein expressions, he helped decipher the codons of the genetic code

1977 – Frederick Sanger develops a technique for rapid DNA sequencing, the Sanger sequencing is also known as chain termination method based on selectively incorporating chain-terminating dideoxynucleotides (ddNTPs)

1984 – Sir Alec Jeffreys developed the multi-locus RFLP probes, a method to compare the variations in DNA of different individuals, leading way to genetic fingerprinting

1986 – The first use of DNA testing in a forensic case, using Jeffreys’ multi-locus RFLP probes for DNA typing to catch Colin Pitchfork, who sexually assaulted and murdered Lunda Mann in 1983 and Dawn Ashworth in 1986

1990 – the Human Genome Project begins, with the goal of mapping all of the 3.3 billion bases of the human genome, and the genome of other organisms, this project costed about $2.7 billion (this amount wasn’t calculated for inflation) and took almost 15 years to complete, compare that to now where it will take about $1000 to sequence the human genome and it will take about a day to do so

2013 – it was discovered that identical (monozygotic) twins actually have differences in their genetic make-up, with differences/mutations called Single Nucleotide Polymorphism (SNPs)

anonymous asked:

Why the strong feels against Watson and crick?

Because of this.

One sentence. Her hard work was STOLEN and they gave her one friggin sentence in the acknowledgement section. Meanwhile they’re riding the cash cow to fame and glory, heralded as these biological geniuses.

It seems like textbooks have become more progressive in the past 5 years or so, but the biology textbook I was issued in high school (published in the early 2000s) dedicated a small, 2-3 sentence paragraph to Rosalind Franklin (which mostly focused on explaining what X-ray crystallography was, not focusing on her contribution or Watson and Crick’s theft of her experimental data), while Watson and Crick received an entire full page spread with their iconic photograph, posing next to a giant DNA model. The most recent version of that textbook now has an entire page dedicated to Rosalind and even includes a picture of her, though!

(Pierce, B. 2012. Genetics: A Conceptual Approach. 4th ed.)

Watson and Crick took credit for Franklin’s work and got away with it because she was a woman. She couldn’t even be awarded the Nobel prize because she died as a result of the radiation from the very X-ray diffraction techniques she used to discover the structure of DNA. Women were not taken seriously in science back then and even still today there is a huge deficit of females in STEM fields.

“Though her features were strong, she was not unattractive, and might have been quite stunning had she taken even a mild interest in clothes. This she did not.” -James Watson

This woman played a crucial role in the discovery of the structure of DNA and Watson said himself that her work with X-ray crystallography was key, but he says her name did not deserve to be on the paper. Why you might ask? Probably because she was a women and only ever look down on during her entire career. She brought the world close to arguable the biggest scientific discovery, yet the only thing she was commented on were her looks. 

Today would have marked Rosalind Elsie Franklin’s 97th birthday, so keep her in your heart. Women in science are still not taken as serious as men. So remember her and what she went through. If you are a women in science follow her example of being strong and confident, if not, respect the women around you and take them seriously! 👩‍🔬🔬💕

Art by @peachistudy 

Discovering the Structure of DNA

On February 21, 1953, Francis Crick and James Watson discovered the structure of deoxyribonucleic acid (DNA) using unacknowledged photographs and research by their colleague Rosalind Franklin. They had considered many other candidates for the structure, including single and triple strand helices before deciphering the structure. Franklin’s x-ray crystallography (image below)

 would provide the missing essential clue they needed to decipher the structure.  They would publish a paper that same year describing their discovery, but the significance of the discovery was largely overlooked by the general public for over a year. Today it stands as one of the most remarkable milestones in the history of science.

The word deoxyribonucleic is a compound word formed around the main root word ribose, which arrived in English in 1892 via the German word Ribose which was itself borrowed from the English word of 1880 arabinose, a sugar derived from gum arabic. The word nucleic comes from the Latin word nucleus meaning a kernel around 1700, from the Latin diminutive nucula meaning a little nut. It did not take the meaning of a central characteristic or attribute until 1762. It wasn’t applied to cellular structures for another 70 years around 1862. The -oxy- root comes from the Ancient Greek word οξυς (oxys) meaning sharp or pointed (sharing the earlier common root word that gave the Latin word acer with the same meaning and ultimately the English word acid). The de- prefix is a Latin preposition meaning down from, off or away from, used mainly in English compound words as a privative, meaning that something lacks something.

Quadruple bonds

Group 6 dinuclear compounds have been of interest have been of interest for over 40 years due to their formation of metal to metal quadruple bonds, σ2π4δ2 [1], with bond order ranging from 0 to 4. The δ bonds are formed from overlap of the dxy orbitals from each metal forming a bonding and antibonding orbital, where z is the internuclear axis. These orbitals are considerably more diffuse and therefore achieve poorer overlap resulting in an order of bond strength of σ> π> δ.[2]

A pair of d4 transition metals can achieve a bond order of 4[1] by filling the σ, π and δ bonding orbitals with no extra electrons in the anti-bonding orbitals, such as in [Re2Cl4].[2]

This is in contrast to the bond orders found in organic chemistry which ranges from 0 to 3, which is a direct consequence of the number s and p orbitals used in bonding.

 Figure 1.[3] (a) Paddle-wheel structure of a dinuclear compound with 4 bridging ligands, Mo2X4 such as [Mo­2­(O­­2CCH3)4]. (b) Structure of Mo2X8 such as K4[Mo2Cl8].2H2O. © Structure of Mo2X4L4 with D2h symmetry.[4,5]

Quadruple bonded metals then form 4 further bonds to ligands, depending on the nature of the ligands, this creates different structures. [Mo­2­(O­­2CCH3)4] has a quadruple bond, high in electron density, is of particular interest due to its particular, due to its unique paddle-wheel structure, spectroscopic properties and potential to be used as a reducing agent.[6]

Over a thousand Mo-Mo compounds have been reported and structures determined using various analytical techniques such as Raman spectroscopy[7], NMR[8] and X-ray crystallography.[1] The Mo-Mo bond length has been extensively researched. The bond length, and thereby bond strength has been determined by X-ray crystallography for 467 compounds containing a Mo-Mo quadruple bond, of which, 442 were within the range 2.06 Å- 2.07 Å.[1] Aforementioned compound [Mo­2­(O­­2CCH3)4] has a Mo-Mo bond length of 2.09 Å [1] and K4[Mo2Cl8].2H2O has a Mo-Mo bond length. [1] This experiment aims to investigate a series of dinuclear Mo compounds containing quadruple bonds and to characterise using NMR and IR.[4]

One of the uses of NMR is to investigate the arrangement of ligands in structure C, Mo2X4L4such as {Mo2Cl4[(C4H9)3]4}. The cis- and trans- forms are of two different symmetry groups and therefore are expected to have different NMR spectrum.[5]


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kinksheriff  asked:

Hey, first off, I love your blog. Additionally, how do you think Medic would respond to the discovery of DNAs structure? Watson and Crick created the model in 1953, which quasi fits in with his timeline.

Well, obviously that would be really exciting to anyone in medical research during that time! However, I like to think that he’d want the contributions of Rosalind Franklin to be recognized alongside Watson and Crick, seeing as her data was critical to their success and glossed over for decades after.

If not for Franklin’s expertise in X-ray crystallography, Watson and Crick might never have clued into the double helix model. At one point, they were told to not even bother with their DNA research because their models were so off! I think Medic would’ve identified with a determined individual researcher like Rosalind Franklin.

Not that she would’ve been able to collect the Nobel Prize she deserved, anyway, since she died of ovarian cancer in 1958, four years before Watson and Crick got the honor. (The Nobel Foundation doesn’t award people posthumously.) Not that accolades are the most important thing. It’s just not fair.

Awesome Women + Google Doodles

Scientists, Mathematicians, and Inventors

Rachel Louise Carson (1907-1964)

American marine biologist and conservationist whose writing brought public attention to environmental threats, especially pesticides

Marie Curie (1867-1934)

Polish and French physicist  and chemist whose pioneering work on radioactivity made her the first woman to win a Nobel prize, as well as the first person and only woman to win two

Rosalind Franklin (120-1958)

An English chemist whose work with x-ray crystallography was instrumental to discovering the structures of DNA, viruses, coal, and graphite; she died of breast cancer before she could be awarded the Nobel prize, and her colleagues Watson and Crick are often given sole credit to this day

Maria Gaetana Agnesi (1718-1799)

Italian mathematician and philospher who wrote first book covering both integral and differential calculus and spent the latter half of her life on charity and theology

Ada Lovelace (1815-1852)

British mathematician and writer whose work on the the Analytical Engine, an early computer, made her the world’s first computer programmer

Feminists and Activists

May Ziade (1886-1941)

Lebanese-Palestinian writer, poet, and translator influential in the Arab literary world and known as an early Palestinian feminist

Henrietta Edwards (1849-1931)

Canadian activist and reformer who fought for women’s rights in voting, education, work, and health

Dorothy Irene Height (1912-2010)

educator and activist who fought for the equal treatment of women, people of color, and LGBT+ people

Concepción Arenal (1820-1893)

Spanish writer and women’s rights activist who was the first woman to attend university in Spain

Emmeline Pankhurst (1858-1928)

British women’s rights activist and suffragette whose militant tactics were key to winning women voting rights in Britian

Artists, Writers, Pilots, One Athlete, and One Entrepreneur

Sohair El-Qalamawy (1911-1997)

influential Egyptian writer, politician, and women’s rights activist, as well as first female professor at Cairo University

Loftia El Nady (1907-2002)

Egyptian aviator who studied flying in secret and became the first female pilot in the Arab world and Africa

Grete Waitz (1953-2011)

Norwegian runner, first woman to run the marathon in under 2.5 hours, and winner of a record 9 New York City Marathons

Amalia Eriksson (1824-1923)

Swedish entrepreneur who became one of the first women in Sweden to own a business and the first person to manufacture peppermint candy

Amelia Earhart (1897-1937)

American aviator and first female pilot to fly across the atlantic

Martha Graham (1894-1991)

American modern dancer and choreographer whose work revolutionized dance and theater

Anne-Cath. Vestly (1920-2008)

Norwegian author of children’s literature whose writing challenged gender roles

M. S. Subbulakshmi (1916-2004)

renowned Indian musician and vocalist who was awarded the  Bharat Ratna and the Ramon Magsaysay award

Nellie Melba (1861-1931)

soprano opera singer who became the first Australian to gain international recognition as a classical musician

                       Happy International Women’s Day!

Happy Birthday Dorothy Hodgkin (May 12)

Dorothy Hodgkin was a Nobel Prize winner who developed the technique of protein crystallography, confirmed the structure of penicillin and vitamin B12, was generally the pioneering figure in the field of X-ray crystallography of biological molecules. Even cooler, she taught Prime Minister Margaret Thatcher (who had a BS in Chemistry from Oxford).

((at least 3 important science & medicine people born on May 12))

Ok so some of you remember the crystallization stuff from my field study that I posted

Well it turns out today I got to take a much closer look at the crystals I made and shoot them through the X-ray machine.

So here’s one of the tubes with the MANY crystals of hemoglobin (with the drug). I showed you something like that last week.

I got to use the microscope to look at them up close and pick a good enough crystal to shoot through the X-ray diffraction machine. 


So the crystal we picked went under a glycerin/mother liquor solution to protect it from breaking down. (Below: the crystals on the left, the solution on the right, and the original mother liquor is behind the solution) 

Mother liquor is the liquid leftover after a crystallization btw.

So the crystal was picked up with a really tiny “lasso” tool so it could be hooked up onto the X-ray machine.

That tiny, pointy thing has a REALLY small hoop at the tip of it to pick the crystal up.

here’s a pic of it up close; that’s how small the hoop and crystal is

and this is the X-ray diffraction machine. 

The crystal is held up here:

and this “shoots” towards the crystal which lets it’s X-rays scatter and that gives us information on the crystalline structure. That ultimately lets us know about the structure of the individual molecules. 

Here’s an up close look at the crystal that was picked:

That’s after it was mounted on the X-ray machine. It’s hard to see cause it’s in front of the black screen.

and that’s the “X-ray” of the crystal we got. The individual dots are the individual components of the crystal. (We actually diffracted a second crystal to get a better x-ray because the dots were too close together on this one). This basically lets us see each unit cell of the crystal itself which would contain a repeat of the hemoglobin molecule with the drug/compound in this case.

By next week, I’ll be able to take a look at the actual protein structure of the Hb molecule and the drug and see how they bind together.

since the factual content of the debate is too microscopic to be imaged directly, I’m attempting to infer it by analysis of the discourse that bounces off, like x-ray crystallography


The plan was to grow a single crystal from this compound for a single crystal X-ray crystallographic analysis to know the exact structure of the compound. But sadly it only gave these fluffy needle like crystals from every solvent what could be used for it’s crystallization. 

Good point: it looks great on a photograph(:

Now every photo what is tagged as my #portfolio, including these crystals, could be purchased as a high quality print at Society6, now with a FREE Worldwide Shipping and $5 discount. To get a on your wall, visit: https://society6.com/labphoto?promo=NJYKQ8VB9QKT

Dorothy Hodgkin (1910-1994) was a British chemist who in 1964 won the Nobel Prize for her development of protein crystallography. She advanced a technique used to determine the three-dimensional structure of molecules, and confirmed the structures of penicillin and of the vitamin B12.

She is seen as a pioneer in the field of X-ray crystallography, and her extensive work led to a better understanding of the structure of biological molecules. Years after winning the Nobel, she was also able to decipher the structure of insulin.

s-c-i-guy  asked:

In Rosalind Franklin's crystallography experiment, how did the DNA strand not get destroyed by the high energy X-rays used?

I worked with crystallographers for like seven years, and I’m still convinced it’s 95% magic.

In x-ray crystallography experiments, you don’t shine the x-ray beam on one single DNA strand, or protein, or whatever it is you’re looking at. One DNA strand would certainly be obliterated by the beam, but not necessarily the crystal (although, often, the x-ray does annihilate your sample. That’s why you need more than one, which makes it even harder).

Instead of a single molecule, it’s a solid crystal, precipitated out of a complex solution of sometimes more than a dozen chemicals, with each crystal made of bajillions and bajillions of individual molecules arranged in an organized lattice. Different crystal structures, whether they are cubes, or tetrahedrons, or hexagonal pyramidal pentaglobs, will act differently in the beam. You don’t know in advance what you’re gonna get.

The protein crystals we used to look at back in my Ph.D. lab looked a lot like this:

Actually, if we’re being honest, they usually didn’t look like that. This is the sort of crystal you dream of. Most things aren’t quite this tidy when they crystallize.

When the x-ray beam is directed at the crystal, it diffracts (bounces off of) any atoms in its way. But x-rays have super-short wavelengths, and molecules are mostly empty space, so only a small fraction of the x-ray waves encounter an atom to bounce off of.

It’s the sum of ALL the rare bouncing events, in the entire crystal, organized into its repeating, ordered structure, that creates the x-ray dot pattern. Then the real fun begins, which as any x-ray crystallographer (and I am not one) will tell you, involves lots of math, and a fair bit of magic.

Women of Science: Dorothy Crowfoot Hodgkin

Not only is inequality damaging for individuals, it also vandalises society as a whole.

This begs the question: what has society missed out on because of inequality?

This is a small testament to those women who somehow managed to throw off the shackles of oppression and change the scientific world.

Women of Science:

Dorothy Crowfoot Hodgkin

A Cairo born British Biochemist, Dorothy Hodgkin has an impressive CV which includes a Nobel prize, the Order of Merit and is the only woman to have received the Copley medal.

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22:05 26.11.15

//Yo Yo guys, I just started a new blog dedicated to my crystallography, so please check it out and give it a follow for some beautiful and interesting chemistry! I will try to link it below. Fingers crossed, i’m not good at formatting posts. This shot is an early shot of one of Macke’s copper sulfate crystal clusters! Now a single crystal has been grown to a length of around 7-8cm. She has talent that girl and its a pleasure to work with her.//