Do Radiation Oncology Residents Have a Preferred Radiation Treatment Planning Review Format?

In an era of increasing virtual communication, we aimed to investigate current formats used by radiation oncology residents for reviewing radiation treatment plans with attendings, preferences for formats, and reasons contributing to preferences. Residents enrolled in Canadian radiation oncology programs received questionnaires examining training level, typical review formats, preferred format, and reasons for preference. Analysis excluded PGY-1s due to insufficient exposure. Fifty-two residents participated. National response rate was 55%. Overall, hybrid review was the most used format (77%). Virtual review was the most preferred format (44%). Preference for virtual review was most common among junior residents (57%), while in-person review was most preferred by senior residents (45.4%). Few residents typically use their preferred format (35%). Reasons for preference varied between groups in convenience (p < 0.01), interactivity (p < 0.01), and teaching quality (p = 0.04). The persistence of e-learning suggests that virtual treatment planning education will continue to some degree. Junior residents prefer virtual review, while a clearly preferred review format was less apparent among senior residents. Preferences are multifactorial, and the trends seen in reasons for preference between formats may reflect advantages inherent to each. Progress is still needed in optimizing treatment planning education, as suggested by few residents using their preferred format. Residents and staff should collectively decide which educational format for treatment planning best meets educational needs.

An investigation of the pH dependence of copper-substituted anthrax lethal factor and its mechanistic implications

Anthrax lethal factor (LF) is a zinc-dependent endopeptidase involved in the cleavage of proteins critical to the maintenance of host signaling pathways during anthrax infections. Although zinc is typically regarded as the native metal ion in vivo, LF is highly tolerant to metal substitution, with its replacement by copper yielding an enzyme (CuLF) 4.5-fold more active than the native zinc protein (at pH 7). The current study demonstrates that by careful choice of the buffer, ionic strength, pH and substrate, the activity ratio of CuLF and native LF can be increased to >40-fold. Using a fluorogenic LF substrate, such optimized assay conditions can be exploited to detect LF concentrations as low as 2 pM. In contrast to the zinc form, CuLF was found to be inhibited by bromide and iodide ions, to be resistant to metal loss under acidic conditions, and to display a sharp pH dependence with significantly shifted alkaline limb towards more acidic conditions. The alkaline limb in the enzyme's pH profile is suggested to originate from changes in the protonation state of the metal-bound water molecule which serves as the nucleophile in the catalytic mechanism. Based on these observations and studies on other zinc proteases, a minimal mechanism for LF is proposed.