A killer is lurking in the waters off the pacific coast. Silent and lethal, it leaves its decimated victims in tidal pools. They first began to appear in the early summer of 2013. Limp and curled, missing some or all of their limbs, the bodies were little more than globs of slimy tissue. They were hardly recognizable as what they once were—Sea Stars. Continue reading
MicroRNAs (miRNAs) are short strands of RNA averaging between 19-24 nucleotides in length that were first discovered in C.elegans and subsequently shown to exist in species ranging from algae to humans (1). Speculated to be merely “junk” more than a decade ago, miRNAs have emerged as powerful regulators of a wide array of cellular processes because of their influence on gene expression at the posttrancriptional level. Dysregulation of these miRNAs is also associated with life-threatening conditions such as cancer and cardiovascular disease, which points to a potential use of miRNAs in diagnosis and treatment. Recently, it has been demonstrated that miRNAs are present in circulating blood plasma, protected from degradation by inclusion in lipid or lipoprotein complexes. This opens up the possibility to exploit miRNA as a useful diagnostic tool in clinical samples. Continue reading
Reporter assays using a single reporter, be it from a stable cell line or transient transfection, can benefit from normalization. Obviously, we are not talking about adding a second control reporter but normalizing to the number of live or dead cells in the well. Two cell health assays, CellTiter-Fluor™ Cell Viability Assay and CellTox™ Green Cytotoxicity Assay, are ideally suited for multiplexing with reporter assays. Continue reading
2015 is the International Year of Light, and activities around the globe are planned to celebrate light in nature, the scientists who have helped us understand the nature of light and the engineers who have developed countless tools and technologies harnessing the power of light. At Promega, our favorite kind of light in nature is bioluminescence. So your Promega Connections bloggers thought we would share this incredible National Geographic video of ocean bioluminescence. In this video, starlight cameras capture the bioluminescence of the ocean, revealing an amazingly beautiful lightscape that is invisible to the unaided human eye. Enjoy!
Interested in Learning More? Check out these Bioluminescence-Related Blog Posts:
Consider the microRNA. At only about 21–26 nucleotides in length, microRNAs (miRNAs) are short, but don’t dismiss miRNAs as too short to accomplish much of anything. miRNAs are a multifunctional workhorse that play a key role in a number of genetic regulatory mechanisms throughout the plant and animal kingdoms and even in certain viruses. Scientists estimate that the human genome encodes about 2,000 different miRNAs and miRNAs account for about 3–4% of human genes (1).
Next Tuesday, we invite you to consider the microRNA with us as we host a webinar discussing the growing field of miRNA research and highlight a new, simplified miRNA purification method. Follow the link below to register.
Presented by Douglas Horejsh, Ph.D.
Tuesday, January 27
- Valinezhad Orang, A., Safaralizadeh, R. and Kazemzadeh-Bavili, M. (2014) Mechanisms of miRNA-mediated gene regulation from common downregulation to mRNA-specific upregulation. Int. J. Genomics Article ID 970607 http://dx.doi.org/10.1155/2014/970607
Many studies, from reporter assays to protein localization to BRET and FRET, require successful transfection first. Yet, transfection can be tricky and difficult. There are many considerations when planning transfection of your cells including reagent selection, stable or transient experiment, type of molecule and endpoint assay used. Here we discuss these considerations to help you plan a successful transfection scheme for your experimental system. Continue reading
When I was in the lab, we usually started with an elaborate system of borrowed hairdryers and old chemistry ring stands. What is your preferred method of attacking a frost-full freezer?
A basic tenet of immunology is that antibodies produced by B cells are very important and specific immunoprotective agents, released in response to infection.
However, antibodies do not supply immediate protection. The invading organism needs to get into the host, meet up with T cells and then B cells, in order for antibody production to occur. If the host has seen this particular pathogen previously, the antibody response occurs somewhat more quickly, but we’re still talking about days. If the invading organism is a bacterium, it can multiply and double in numbers in just hours. Thus an infection could potentially gain a foothold in a body prior to an antibody response.
Fortunately we have a more rapid, first line of defense to invading pathogens, a cellular response. In the case of a puncture or skin wound, epithelial cells, mast cells and leukocytes are activated quickly in response to pathogens. Neutrophils and monocytes also aid the cellular response.
Now a recently published report demonstrates that fat cells also play a part in the cellular response to invading bacteria. R. Gallo et al. published a study on Jan. 2 in Science, providing more in depth information on the role of adipocytes in the host response to the bacterium Staphylococcus aureus (S. aureus). Continue reading
N-Glycosylation is a common protein post-translational modification occurring on asparagine residues of the consensus sequence asparagine-X-serine/threonine, where X may be any amino acid except proline. Protein N-glycosylation takes place in the endoplasmic reticulum (ER) as well as in the Golgi apparatus.
Approximately half of all proteins typically expressed in a cell undergo this modification, which entails the covalent addition of sugar moieties to specific amino acids. There are many potential functions of glycosylation. For instance, physical properties include: folding, trafficking, packing, stabilization and protease protection. N-glycans present at the cell surface are directly involved in cell−cell or cell−protein interactions that trigger various biological responses.
The standard method used to profile the N-glycosylation pattern of cells is glycoprotein isolation followed by denaturation and/or tryptic digestion of the glycoproteins and an enzymatic release of the N-glycans using PNGase F followed by analysis mass spec. This method has been reported to yield high levels of high-mannose N-glycans that stem from both membrane proteins as well as proteins from the ER.(1,2)
For those researchers interested in characterizing only cell surface glycans (i.e., complex N-glycans) a recent reference has developed a model system using HEK-292 cells that demonstrates a reproducible, sensitive, and fast method to profile surface N-glycosylation from living cells (3). The method involves standard centrifugation followed by enzymatic release of cell surface N-glycans. When compared to the standard methods the detection and quantification of complex-type N-glycans by increased their relative amount from 14 to 85%.
- North, S. J. et al. (2012) Glycomic analysis of human mast cells, eosinophils and basophils. Glycobiology. 2012, 22, 12–22.
- Reinke, S. O. et al. (2011) Analysis of cell surface N-glycosylation of the human embryonic
kidney 293T cell line. J. Carbohydr. Chem. 30, 218–232.
- Hamouda, H. et al. (2014) Rapid Analysis of Cell Surface N‑Glycosylation from Living Cells Using Mass Spectrometry. J of Proteome Res. 13, 6144–51.
Monday lab meeting? Journal club? Long weekend in the lab?
Enjoy this classic from the Promega Cartoon Lab.