Florence Bell—the ‘Housewife’ with x-ray vision

2021 ◽  
Author(s):  
Kersten Hall
Keyword(s):  
Helical Structure ◽  
Ordered Structure ◽  
Mars Rover ◽  
X Ray ◽  
Double Helical Structure ◽  
Award Winning

After an award-winning portrayal by Nicole Kidman in a hit West End play, a Mars Rover named in her honour, and recently a commemorative 50 pence coin released by the Royal Mint, Rosalind Franklin's crucial work in the discovery of the double-helical structure of DNA is well recognized. Far less well known, however, is the name of Florence Bell, the crystallographer who first showed that X-ray analysis could be used to reveal the regular, ordered structure of DNA. This paper explores her life and work, the legacy of which is ‘Photo 51’, the famous X-ray image of DNA taken by Rosalind Franklin and Raymond Gosling in 1952 that now features on the new 50 pence coin.

Address of the President Sir Alan Hodgkin, O. M. at the Anniversary Meeting, 1 December 1975

1976 ◽  
Vol 192 (1109) ◽  
pp. 371-391
Keyword(s):  
Molecular Biology ◽  
Coiled Coil ◽  
Helical Structure ◽  
X Ray Diffraction ◽  
Helical Structures ◽  
X Ray ◽  
Double Helical Structure ◽  
Leading Role ◽  
Replication Scheme ◽  
Related Proteins

The Copley Medal is awarded to Dr F. H. C. Crick, F. R. S. In 1953 Crick and Watson proposed the double-helical model for DNA, in which the bases are arranged in complementary pairs so that the molecule is capable of self-replication and is thus the essential carrier of genetic information in living cells. This proposal was based on an inspired interpretation of the results of X-ray diffraction analysis of DNA carried out by Wilkins, Franklin and their collaborators, and on the chemical analyses of Chargaff and others. The replication scheme inherent in the double-helical structure of DNA made it possible for the first time to discuss the mechanism of heredity in molecular terms; it has been the most fruitful concept in the whole of biology during the past 25 years, and has been the basis for the explosive development of molecular biology. Besides his part in this dramatic discovery, Crick played a very important part in increasing our understanding of the way in which the genetic message is carried on DNA (the ‘coding’ problem), and of the mechanisms by which it is translated into specific sequences of amino acids in the proteins synthesized by the cell. He has also continued to play a leading rôle in many other aspects of molecular biology, and has made important contributions to X-ray studies of crystalline proteins, fibrous proteins and viruses. These include the theory of diffraction from helical structures, the coiled-coil model of α-keratin and related proteins, the structure of collagen, and the theoretical basis of the construction of ‘spherical’ viruses. More recently, Crick has had an important influence on work in the fields of development and of chromosome structure.

DNA polymorphism in crystals: three stable conformations for the decadeoxynucleotide d(GCATGCATGC)

2016 ◽  
Vol 72 (6) ◽  
pp. 780-788 ◽  
Author(s):  
Arunachalam Thirugnanasambandam ◽  
Selvam Karthik ◽  
Gunanithi Artheswari ◽  
Namasivayam Gautham
Keyword(s):  
Metal Ion ◽  
Helical Structure ◽  
Mixed Population ◽  
Helical Conformation ◽  
Cd Spectra ◽  
X Ray ◽  
X Ray Crystallography ◽  
Double Helical Structure ◽  
Flexible Molecule ◽  
Dna Fragment

High-resolution structures of DNA fragments determined using X-ray crystallography or NMR have provided descriptions of a veritable alphabet of conformations. They have also shown that DNA is a flexible molecule, with some sequences capable of adopting two different structures. Here, the first example is presented of a DNA fragment that can assume three different and distinct conformations in crystals. The decanucleotide d(GCATGCATGC) was previously reported to assume a single-stranded double-fold structure. In one of the two crystal structures described here the decamer assumes both the double-fold conformation and, simultaneously, the more conventional B-type double-helical structure. In the other crystal the sequence assumes the A-type double-helical conformation. These results, taken together with CD spectra, which were recorded as the decamer was titrated against four metal ions and spermine, indicate that the molecule may exist as a mixed population of structures in solution. Small differences in the environmental conditions, such as the concentration of metal ion, may decide which of these crystallizes out. The results also support the idea that it may be possible for DNA to change its structure to suit the binding requirements of proteins or drugs.

scholarly journals Double helical structure of the twist-bend nematic phase investigated by resonant X-ray scattering at the carbon and sulfur K-edges

Soft Matter ◽  
2018 ◽  
Vol 14 (48) ◽  
pp. 9760-9763 ◽  
Author(s):  
Mirosław Salamończyk ◽  
Richard J. Mandle ◽  
Anna Makal ◽  
Alexander Liebman-Peláez ◽  
Jun Feng ◽  
...  
Keyword(s):  
Nematic Phase ◽  
Helical Structure ◽  
Crystalline Phases ◽  
X Ray ◽  
Double Helical Structure ◽  
X Ray Scattering ◽  
Ray Scattering

Resonant X-ray scattering revealing structural similarities of twist-bend nematic and crystalline phases.

Address of the President Sir Alan Hodgkin, O. M. at the Anniversary Meeting, 1 December 1975

1976 ◽  
Vol 348 (1653) ◽  
pp. 153-173
Keyword(s):  
Molecular Biology ◽  
Coiled Coil ◽  
Helical Structure ◽  
X Ray Diffraction ◽  
Helical Structures ◽  
X Ray ◽  
Double Helical Structure ◽  
Leading Role ◽  
Replication Scheme ◽  
Related Proteins

The Copley Medal is awarded to Dr F. H. C. Crick, F. R. S. In 1953 Crick and Watson proposed the double-helical model for DNA, in which the bases are arranged in complementary pairs so that the molecule is capable of self-replication and is thus the essential carrier of genetic information in living cells. This proposal was based on an inspired interpretation of the results of X-ray diffraction analysis of DNA carried out by Wilkins, Franklin and their collaborators, and on the chemical analyses of Chargaff and others. The replication scheme inherent in the double-helical structure of DNA made it possible for the first time to discuss the mechanism of heredity in molecular terms; it has been the most fruitful concept in the whole of biology during the past 25 years, and has been the basis for the explosive development of molecular biology. Besides his part in this dramatic discovery, Crick played a very important part in increasing our understanding of the way in which the genetic message is carried on DNA (the ‘coding’ problem), and of the mechanisms by which it is translated into specific sequences of amino acids in the proteins synthesized by the cell. He has also continued to play a leading rôle in many other aspects of molecular biology, and has made important contributions to X-ray studies of crystalline proteins, fibrous proteins and viruses. These include the theory of diffraction from helical structures, the coiled-coil model of α-keratin and related proteins, the structure of collagen, and the theoretical basis of the construction of ‘spherical’ viruses. More recently, Crick has had an important influence on work in the fields of development and of chromosome structure.

Characterisation of planar crystal defects in Y2Fe17Cx (0.6 ≤ x ≤ 1.6) magnetic material by High Resolution Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 774-775
Author(s):  
W. Coene ◽  
F. Hakkens ◽  
T.H. Jacobs ◽  
K.H.J. Buschow
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Permanent Magnets ◽  
Annealing Treatment ◽  
High Resolution Electron Microscopy ◽  
Crystal Defects ◽  
Ordered Structure ◽  
X Ray ◽  
Planar Crystal ◽  
Resolution Electron

Intermetallic compounds of the type RE2Fe17Cx (RE= rare earth element) are promising candidates for permanent magnets. In case of Y2Fe17Cx, the Curie temperature increases from 325 K for x =0 to 550 K for x = 1.6 . X ray and electron diffraction reveal a carbon - induced structural transformation in Y2Fe17Cx from the hexagonal Th2Ni17 - type (x < 0.6 ) to the rhombohedral Th2Zn17 - type ( x ≥ 0.6). Planar crystal defects introduce local sheets of different magnetic anisotropy as compared with the ordered structure, and therefore may have an important impact on the coercivivity mechanism .High resolution electron microscopy ( HREM ) on a Philips CM30 / Super Twin has been used to characterize planar crystal defects in rhombohedral Y2Fe17Cx ( x ≥ 0.6 ). The basal plane stacking sequences are imaged in the [100] - orientation, showing an ABC or ACB sequence of Y - atoms and Fe2 - dumbbells, for both coaxial twin variants, respectively . Compounds resulting from a 3 - week annealing treatment at high temperature ( Ta = 1000 - 1100°C ) contain a high density of planar defects.

Quantification of Starch Order in Physically Modified Rice Flours Using Small-Angle X-ray Scattering (SAXS) and Fourier Transform Infrared (FT-IR) Spectroscopy

2021 ◽  
pp. 000370282110282
Author(s):  
Daitaro Ishikawa ◽  
Jiamin Yang ◽  
Tomoyuki Fujii
Keyword(s):  
Infrared Spectroscopy ◽  
Small Angle ◽  
Water Sorption ◽  
Order Parameter ◽  
Rice Flour ◽  
Ordered Structure ◽  
X Ray ◽  
Glucose Unit ◽  
X Ray Scattering ◽  
Ray Scattering

The purpose of this study was to understand the ordered structure of starch in rice flour based on a physical modification with non-heating, milling, and water sorption through the structural evaluation of rice flour using small-angle X-ray scattering (SAXS) and infrared spectroscopy within the 4000–100 cm−1 region. The SAXS pattern of the samples with low moisture contents subjected to milling yield a band within the 0.4–0.9 nm−1 of the q range owing to a lamellar repeat of starch with an ordered structure in rice flour. We proposed an order parameter using the intensity of the SAXS band to quantify the order structure of starch in rice flour, and the true density was negatively correlated with the order parameter. Infrared band at 990 cm−1 in COH bending mode applied to the hydroxyl group of C6 shifted to a low wavenumber corresponding to the order parameter. A linear correlation was found between the order parameter and the 990 cm−1 and band at 861 cm−1 owing to COC symmetrical stretching of glycoside bond and CH2 deformation of the glucose unit of starch, 572, 472, and 436 cm−1, owing to the pyranose ring in the glucose unit of starch. The identified infrared bands are effective for quantifying the ordered structure of starch at the lamellar level. When subjected to water sorption, the band position at 990 cm−1 shifted to a higher wavenumber above a water activity of 0.7. This result revealed that the water-induced transition of glass to rubber of starch in rice flour can be clearly evaluated through infrared spectroscopy using the band at 990 cm−1. In addition, the band at 861 cm−1 also shifted to a higher wavenumber, whereas those at 572 and 436 cm−1 did not show a significant shift. These results indicate that water sorption slightly affects the internal structure and may mainly affect the surface of starch.

scholarly journals Living supramolecular polymerization of fluorinated cyclohexanes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Oleksandr Shyshov ◽  
Shyamkumar Vadakket Haridas ◽  
Luca Pesce ◽  
Haoyuan Qi ◽  
Andrea Gardin ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Self Assembly ◽  
Materials Science ◽  
Helical Structure ◽  
The Self ◽  
Supramolecular Polymers ◽  
Aliphatic Compound ◽  
Double Helical Structure ◽  
Key Driver ◽  
Supramolecular Polymerization

AbstractThe development of powerful methods for living covalent polymerization has been a key driver of progress in organic materials science. While there have been remarkable reports on living supramolecular polymerization recently, the scope of monomers is still narrow and a simple solution to the problem is elusive. Here we report a minimalistic molecular platform for living supramolecular polymerization that is based on the unique structure of all-cis 1,2,3,4,5,6-hexafluorocyclohexane, the most polar aliphatic compound reported to date. We use this large dipole moment (6.2 Debye) not only to thermodynamically drive the self-assembly of supramolecular polymers, but also to generate kinetically trapped monomeric states. Upon addition of well-defined seeds, we observed that the dormant monomers engage in a kinetically controlled supramolecular polymerization. The obtained nanofibers have an unusual double helical structure and their length can be controlled by the ratio between seeds and monomers. The successful preparation of supramolecular block copolymers demonstrates the versatility of the approach.

scholarly journals Accurate Representation of B-DNA Double Helical Structure with Implicit Solvent and Counterions

2002 ◽  
Vol 83 (1) ◽  
pp. 382-406 ◽  
Author(s):  
Lihua Wang ◽  
Brian E. Hingerty ◽  
A.R. Srinivasan ◽  
Wilma K. Olson ◽  
Suse Broyde
Keyword(s):  
Helical Structure ◽  
Implicit Solvent ◽  
Accurate Representation ◽  
Double Helical Structure

Direct-to-Consumer Genetic Testing

2011 ◽  
pp. 51-84 ◽  
Author(s):  
Richard A. Stein
Keyword(s):  
Human Genome ◽  
Human Genome Project ◽  
Cost Effective ◽  
Helical Structure ◽  
Genome Project ◽  
Next Generation ◽  
Double Helical Structure ◽  
Sequencing Technologies ◽  
Human Genome Sequencing ◽  
The Human Genome Project

The 1953 discovery of the DNA double-helical structure by James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin, represented one of the most significant advances in the biomedical world (Watson and Crick 1953; Maddox 2003). Almost half a century after this landmark event, in February 2001, the initial draft sequences of the human genome were published (Lander et al., 2001; Venter et al., 2001) and, in April 2003, the International Human Genome Sequencing Consortium reported the completion of the Human Genome Project, a massive international collaborative endeavor that started in 1990 and is thought to represent the most ambitious undertaking in the history of biology (Collins et al., 2003; Thangadurai, 2004; National Human Genome Research Institute). The Human Genome Project provided a plethora of genetic and genomic information that significantly changed our perspectives on biomedical and social sciences. The sequencing of the first human genome was a 13-year, 2.7-billion-dollar effort that relied on the automated Sanger (dideoxy or chain termination) method, which was developed in 1977, around the same time as the Maxam-Gilbert (chemical) sequencing, and subsequently became the most frequently used approach for several decades (Sanger et al., 1975; Maxam & Gilbert, 1977; Sanger et al., 1977). The new generations of DNA sequencing technologies, known as next-generation (second generation) and next-next-generation (third generation) sequencing, which started to be commercialized in 2005, enabled the cost-effective sequencing of large chromosomal regions during progressively shorter time frames, and opened the possibility for new applications, such as the sequencing of single-cell genomes (Service, 2006; Blow, 2008; Morozova and Marra, 2008; Metzker, 2010).

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