The human body is a fascinating wonder in which billions of processes are constantly occurring. Proteins play an important role in all of these processes. As an analytical chemist, I am studying the protein content of various body fluids, such as blood or saliva, in order to understand and find early signs of disease and to investigate factors influencing communication, regulation and growth in healthy human cells. This work has implications in medicine, biology and chemistry.

All human cells contain a genome, which is the genetic information inherited from our parents. The genome is the cell blueprint, like the construction design for a house. The actual house is built out of proteins, "the building blocks of our bodies". Proteins are responsible for such diverse things as building our muscles and skin, digestion of food, cell growth and human emotions. There is a protein involved in almost any process one can imagine. Our bodies are constantly producing proteins. Sometimes malfunctions in the production process lead to new or changed proteins. In most cases, this has little or no effect in our bodies. However, in rare occasions, the changed protein leads to a better function in the body, commonly known as evolution. And in some unfortunate cases, a changed protein leads to a disease, such as Alzheimer's disease or Parkinson's disease.

In my research I am looking at the protein content in various body fluids including blood, urine, saliva and cerebrospinal fluid (the fluid surrounding the brain). These body fluids contain an enormous number of different proteins as well as other substances. Proteins are complex molecules and in order to identify them correctly one must often break them down into smaller fragments, called peptides. Each protein consists of many peptides, which are often specific for just that protein. For instance, the analysis of cerebrospinal fluid can be compared to taking your favorite book and mixing up all the words into a gigantic bowl of alphabet soup. One must first pick out each word and create sentences, paragraphs and chapters. Each sentence, paragraph and chapter must be arranged correctly in order for the story to read well.

Why measure the content of proteins and peptides in human body fluids? Well, as mentioned before, proteins and peptides play an important role in almost every process in the body and can be the root of disease. The concentration of a protein might be increased or decreased, or new proteins might appear as a consequence of a certain disease. The study and comparison between patients suffering from a disease and healthy people might reveal the cause of the disease. It is important to understand why a certain disease occurs and in an early state identify the signs for that disease to efficiently treat it. Beyond the treatment of disease, there is great interest in how healthy cells function. Ultimately, researchers will understand the role of individual proteins and how they work together to regulate the body. Returning the analogy of a house, this could be compared to standing at the construction site of a building and studying where each piece goes and how they come together to support the house.

How is this analysis conducted in the lab? First the, peptides are "picked out" or separated from each other. The separation is performed in an extremely small tube of glass. Under the influence of a strong electrical field, the peptides will move through the tube at different speeds. This separation technique, which takes advantage of the differences in speed, is called capillary electrophoresis. Second, the identity and amount of each peptide must be determined. This is done with a mass spectrometer. The mass spectrometer measures each peptide's mass-to-charge ratio. From the information obtained by the mass spectrometer one can determine the structure and mass of each peptide.

The detected peptides are then matched against databases containing peptide sequences of known proteins (imagine comparing the fragments from the book we destroyed to a database of possible sentences). This is done to identify the peptides and the proteins from which they came. The database matching is tedious and time consuming and thus there is a great need for fast and powerful computers and reliable databases. After peptide and protein matching is completed, it is up to the analysts to find trends in the results. Based on these trends, they then develop theories about the role specific proteins may play in the body.

My own research focuses on improving methods for separating and detecting proteins. I have refined the ways to separate and transfer the peptides from the glass tube to the mass spectrometer. Medical, biological and chemical researchers are now using my methods.

I am interested in finding out how proteins communicate with each other. I do this by gently attaching proteins to one side of a thin layer of gold and bouncing light off the other side. By watching changes in the reflected light as different proteins are presented to the attached proteins, I can see which proteins interact, how fast they interact, and how strongly they interact. Because of the importance of proteins to health, these studies can reveal which drugs might be effective in treating disease, or unravel questions about how proteins function in the body.

Proteins are one of the building blocks of all living things. They are vital to everything an organism does, from moving, to thinking, to digesting food. I am interested in one particular activity of proteins, which is communicating with each other. I use a technique that, like eavesdropping, enables me to hear the proteins' conversations without interrupting them. The technique relies on the fact that not all proteins are interested in each other. For their biological function, proteins have developed to recognize some proteins while completely ignoring others. Often, recognition is followed by some change in the protein's shape, which enables it to do a different job, such as make a needed material or transmit a signal from one part of its environment to another.

The protein I am currently examining is found in the heart and is responsible for the adrenaline rush. If you get into a life-threatening situation, this protein will respond to the flood of adrenaline in your system and prepare your body to fight or to flee. The protein is called a receptor because it receives a signal from adrenaline. There are many different kinds of receptors, which receive signals from different things, and as a class of proteins they are vital to the normal function of an organism. Receptors have the interesting task of communicating messages across the cell membrane, the thin skin of the cell that allows only some things to pass through. The membrane keeps the cell's contents in, while keeping the rest of the world out. However, the cell still needs a way to selectively receive information from the world outside, and that is the function of a receptor. Important messages, carried by traveling chemicals, reach the cell membrane, where they pass their message to the receptor in the membrane. By changing its shape, the receptor conveys the message to the cell's interior where it communicates with a different protein that can move around the cell and cause the cell to respond appropriately to the message from the outside. In the case of these adrenaline-sensitive receptors in the heart, the receptor interacts with adrenaline from the outside and conveys the message to another protein on the inside. When many heart cells receive this message at the same time, the heart begins to beat faster, readying the body for the "fight-or-flight" response. Obviously, if the receptor doesn't do its job properly, the heart would not have the right response to the stimulus.

To eavesdrop on the proteins, I must let them function normally. This means that rather than handling the proteins directly, I observe them indirectly. I stick one protein to a thin piece of gold. In doing so, I try not to alter the protein, since I want it to be as natural as possible. I then bounce light off the backside of the gold. The gold is so thin that some light penetrates to the other side, where it can see any proteins attached to the gold on the front. The proteins absorb light, so the reflected light is less intense than the original light. As more proteins are added to the layer on top of the gold, the reflected light becomes dimmer. I then introduce different proteins to the environment above the fixed proteins. If they have anything to say to each other, they'll bind together, making the protein layer thicker and the light dimmer.

There are two motivations for the research I do. The first is the fundamental understanding of how proteins work. Proteins are involved in many complex relationships, making them an exciting challenge for scientists. The second motivation is the role of proteins is disease. When proteins go haywire, disease is the inevitable result. In fact, over 50% of therapeutic drugs on the market or in development help receptor proteins to function smoothly. My experiments reveal the complicated conversations among proteins which maintain health, or cause its deterioration.

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Edgar Arroyo
Department of Research
Protengia Institute
March 2005