Theoretical study of redox cofactors of bd cytochromes
Cytochromes bd are proteins implied in cell respiratory mechanism in low oxygen environment of various bacterias. Electronic transfers between three hemes have been found crucial in their functioning. Study of the redox cofactor of these hemes will imply better knowledge of their properties, thus understanding the function of cytochromes bd. A Density Functional Theory approach has been used during this internship among the TeoSim group of the ICP laboratory of the Université Paris-Saclay. First, we have determined the required parameters for the DFT method (functional, basis, Auxillary basis...). Then, the spin state stability study of each heme led us to their geometry optimization in their ground state. Finally, redox properties of hemes in gas phase had been computed and compared to existing experimental data.
Iodine: 210 years of research at the service of society
Discovered by accident at the beginning of the 19th century, iodine quickly became the subject of numerous research projects and applications that have continued to grow over the years. Different from other halogens, it is distinguished by its redox properties, its low electronegativity, its great polarizability and its hypervalence. Iodine is present in everyday life in table salt, in food colouring and in halogen lamps. It plays a key role as a catalyst in the industrial production of acetic acid. It is also widely used in solution chemistry due to its redox properties which make it a redox species of choice. In organic synthesis, the iodation of organic compounds is of great interest and hypervalent iodine compounds are used for their oxidizing properties. In addition to its antiseptic properties and its use in radioprotection and medical imaging, iodine is a trace element that regulates hormonal systems. Iodine deficiency remains a major public health problem today.
Nanomaterials for batteries
Batteries are a well-known technology to store energy. If the first batteries were made at the end of the nineteenth century, major technological issues prevented their development for decades. Today, batteries are regarded as a promising way to store energy from sustainable sources, but their performance still has to be improved. In this article, the use of nanomaterials for batteries is explored and the advantages as well as the current limits of such material is exposed.
Introduction to plasma physicochemistry
Plasma is an unknown medium which however has a lot of applications. Considered as the fourth state of matter, a plasma is produced by ionizing a gas. This medium is far from being artificial as physicists expect 99% of matter in the universe to be in plasma state. On Earth, natural phenomena like lightnings, aurora borealis, neon lights and television screens use plasma. This article aims at popularizing basic notions of plasma physics and chemistry. First, some vocabulary and the different types of plasma will be introduced. Then, the generation of a plasma starting from a gas will be described and the double dielectric barrier geometry will be detailed. Finally, the different chemical reactions occurring in a plasma will be described relying on the example of an air plasma.
Phosphorescent windows - Synthesis of phosphorescent strontium aluminates
When one visits a church, one cannot but stare in awe at the vitrals - usually a centerpiece of the building. However, it is much more difficult to look at them properly at night. We dealt with that issue during the "Tournoi Français des Chimistes", and we will be presenting in this article our thoughts and experiments about creating vitrals that can be lit autonomously at night.
The CMS Experiment at CERN
This article will present the study and the reconstruction of particles thanks to the Compact Muon Solenoid detector. It is one of the four main detectors of the CERN's particle accelerator called 'Large Hadron Collider'. The LHC - which lies near Geneva - is a circular ring used to create high-energy collisions between various entities. Its global fonctioning will be examined first, followed by the study of the CMS detector in details. The different subdetectors of CMS will be presented to understand the concept of 'particle reconstruction'. However some particles are not stable enough to get across the detector. Therefore, their products of disintegration will be observed. By looking at the article 'A measurement of the Higgs boson mass in the diphoton decay channel' by CMS collaboration, the final part exemplifies the reconstruction of particles that are not directly observed such as the Higgs boson.
Apology of a poison: Arsenic, properties and applications
Arsenic is a rare element present in traces on our planet Earth. It is nonetheless known for its surprising properties. These led it to appear very early on among the first elements of the pantheon of alchemy and then that of chemistry, just like gold and sulfur for example, which we find in Lavoisier's classification. Our imagination places it rather as reserved for disastrous uses because of its status as “king of poisons and poison of kings”. Its history is also linked to that of gold in a way that seems fortuitous, but our knowledge of this element has greatly evolved. We now know that it is found at the center of the energy mechanism of certain plants. It has been used by humans as a muscle tonic, or as a medicine against certain types of leukemia, and has entered advanced technology as a semiconductor. Its main properties are discussed here in the geosphere and in the biosphere in relation to its chemical and structural properties.
Nitrogen is a crucial element to study for biogeochemical and climate studies. It is naturally found in organic matter, in DNA and proteins for example, and in inorganic form into the atmosphere and soils. Among inorganic N-bearing species, "NOx" gases are particularly relevant to study and monitor because of their toxicity and mainly anthropic origin. Exchanges between the nitrogen reservoirs are depicted in the Nitrogen Cycle. Nowadays, this biogeochemical cycle is disturbed by human activities. Studies are conducted to reduce the production of NOx and the impact of human activities on the Nitrogen Cycle.
Boron: State of the art
The element Boron is often little-known by the general public, which is surprising considering its wide range of application, in specialised domains of chemistry like in everyday life. Boron possesses peculiar radiochemical properties: It is one of the most efficient neutron absorbents, a property currently put in use by nuclear power plants. Boron can form atypical chemical bonds, called “banana” bonds, which allow inorganic chemists to create compounds which structures only limited by imagination [why does this sound like processed cheese??] With the help of organic chemists, they could boron-based structures capable of entering in cancer cells and absorb neutrons, resulting in enough energy to destroy said cells. Aside from being a lead in cancer therapy, the chemistry of boron allows the appearance of materials with properties controlled over a large range.
Gallium: an overview
Gallium, with its unusually low melting point for a metal, melts in the hand. Its properties enable numerous uses, such as in alloys like gallium arsenide or galinstan, in organic chemistry as a catalyst or a Lewis acid, and in the biomedical sector thanks to the similarities between gallium and iron.