The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu.

The desire to directly probe biological structures on the length scales that they exist has driven the steady development of various high-resolution microscopy techniques. Among these, optical microscopy and, in particular, fluorescence-based approaches continue to occupy dominant roles in biological studies given their favorable attributes. Fluorescence microscopy is both sensitive and specific, is generally noninvasive toward biological samples, has excellent temporal resolution for dynamic studies, and is relatively inexpensive. Light-based microscopies can also exploit a myriad of contrast mechanisms based on spectroscopic signatures, energy transfer, polarization, and lifetimes to further enhance the specificity or information content of a measurement. Historically, however, spatial resolution has been limited to approximately half the wavelength due to the diffraction of light. Near-field scanning optical microscopy (NSOM) is one of several optical approaches currently being developed that combines the favorable attributes of fluorescence microscopy with superior spatial resolution. NSOM is particularly well suited for studies of both model and biological membranes and application to these systems is discussed.

Microdialysis sampling, a well known diffusion‐based separation method, has been used to collect solutes from various tissues in selected organisms. Cytokines have low aqueous diffusion coefficients and can frequently be in low (fM to pM) concentrations. The purpose of this study was to analyze heparin for its ability to increase the RR of selected cytokines. Heparin is a naturally‐occurring glycosaminoglycan and has high binding affinity to many types of cytokines. Two cytokines, monocyte chemoattractant protein‐1 (MCP‐1) and RANTES were chosen since we have confirmed their binding to heparin using surface plasmon resonance (SPR) to be KD = 5.08 ± 1.63 nM and 474 ± 110 nM respectively. For each cytokine, it was important to ensure that heparin did not affect the chemical analysis. Heparin concentrations in the range of 10 µM to 0.001 µM did not interfere with ELISA analysis. In this study, the relative recovery of the cytokine MCP‐1 was shown to increase with heparin concentrations 1 µM (18.34%) and 10 µM (21.20%), but possible interference by heparin of the ELISA analysis was observed. Cytokine RANTES was suspected to cause high dose hook effect with a modified ELISA protocol.