The Human Immunodeficiency Virus type-1 (HIV-1) currently infects 37 million people worldwide, with an additional 2 million new infections each year. Following infection, the virus has a long period of latency, during which it multiplies without causing symptoms. HIV attacks the cells of the immune system, especially the cells called CD4+ T-lymphocytes, which are responsible for triggering the body's response chain against infections. Thus, by suppressing the action of the immune system, the virus destroys the body's ability to defend itself against other diseases, leading to the so-called Acquired Immunodeficiency Syndrome, or AIDS.

Catalysts are materials that promote and accelerate chemical reactions without being consumed during the process. For example, catalysts are used, for example, to reduce the emission of toxic gases, such as the carbon monoxide ($\rm CO$) produced by car engines. The catalytic converters present in the exhaust of vehicles allows the $\rm CO$ oxidation reaction to occur, that is, in the presence of a catalyst, $\rm CO$ reacts with the oxygen gas ($\rm O_2$) leading to the formation of carbon dioxide ($\rm CO_2$).

Cancer is a set of diseases characterized by uncontrolled multiplication of cells. One of the main methods for treating this disease is chemotherapy, which uses drugs to block the growth of those cells or to destroy them. In this way, most drugs used interfere with mitosis, the cellular mechanism by which new cells are produced. Therefore, both cancerous and healthy cells are affected, leading to several side effects.

Tuberculosis is a chronic infection usually caused by a bacterium called Mycobacterium tuberculosis. This bacterium infects cells of the immune system called alveolar macrophages, which are responsible for removing pollutants and microorganisms from the surface of the alveoli, where the exchange of gases occurs during respiration.

Once a disease-related protein or enzyme is identified as a therapeutic target, the study of its three-dimensional structure - the positions of each of its atoms and their interactions - allows a deeper understanding of its mechanisms of action.

This is possible not only for these substances produced by microorganisms, such as viruses or bacteria, capable of attacking our body. It is also possible, for example, to understand molecules normally produced by the human body itself, but which had their structure and function altered due to some genetic mutation.

In agricultural production, several of the nutrients needed for the growth and development of plants are supplied or supplemented by fertilizers. Some nutrients, such as phosphorus ($ \rm P $) and potassium ($ \rm K $), are needed in large quantities, but obtained from limited mineral sources. Others - such as manganese ($ \rm Mn $), copper ($ \rm Cu $) or zinc ($ \rm Zn $) - are only needed in small quantities and the excess can be toxic to plants or to important microorganisms present in the soil. Therefore, there is an intense research into new fertilizers that allow the rational delivery of the nutrients necessary for agriculture, avoiding their use in excessive, inefficient use, or environmentally harmful ways.

Once a disease-related protein is identified as a therapeutic target, the study of its three-dimensional structure - the positions of each of its atoms and their interactions - allows a deep understanding of its action in the body, and its interaction with a potential drug. In this way, it is possible to discover potential new drugs, or to understand the functioning of known drugs and to increase their effectiveness.

The contamination of the atmosphere by gases and solid particles affects not only human health in urban centers but also the ecosystem. The management of air quality depends on several actions including the establishment of quality standards, the regulation of the release of pollutants, and the monitoring of air quality in a given region.

Programs for air quality monitoring can point out levels of pollutants in the atmosphere and assess their compliance with standards set by legislation. However, they are not able to identify the individual contribution of each source responsible for the emission.

The morphology of biological systems has fascinated both architects and scientists, and their reproduction in the nanoscale could be very useful for technological purposes. This type of structure is already considered a candidate for applications in chemical catalysis, air filters for virus elimination, and membranes for water purification and separation of proteins.

The development of electronic devices in the nanometric scale depends on the search for materials that have appropriate characteristics, and that are also efficient and inexpensive. This is the case of graphene, a material formed by a single layer of carbon atoms obtained from graphite. Graphene is a conductor with excellent optical and electrical properties that can be easily altered by the incidence of electric fields or light.