Conformal Dynamic Arcs (CDA) can provide a useful alternative in certain clinical situations which require a higher level of 3-dimensional (3D) conformation than shaped static fields but for which modulated fields (fixed or arc) are inappropriate. Due to lack of modulation, the quality of the dose distribution produced by a CDA is highly dependent on the specific patient geometry. The ideal geometry for a CDA, in terms of achievable conformation and uniformity, is a spherical target perfectly centered in a cylindrical medium or body and utilizing a full 360 degree of rotation. This manuscript will provide or review several methods a treatment planner may employ to improve dose distributions produced by CDA as the patient and/or target geometry or degrees of arc rotation vary from the ideal. These include: 1. Weighting arc segments to improve homogeneity. 2. Defining asymmetric margins for fitting leaves. 3. Hybrid static/CDA compensating for CDA with limited degrees of rotations. 4. Improving conformation in irregular target via use of pseudo-PTV. 5. Creating concave features via the use of avoidance structures. 6. Editing CDA multi-leaf collimator (MLC) to remove irregular hot spots.
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http://dx.doi.org/10.1016/j.meddos.2020.10.003 | DOI Listing |
Proc Natl Acad Sci U S A
February 2025
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea.
The design of organic-peptide hybrids has the potential to combine our vast knowledge of protein design with small molecule engineering to create hybrid structures with complex functions. Here, we describe the computational design of a photoswitchable Ca-binding organic-peptide hybrid. The designed molecule, designated Ca-binding switch (CaBS), combines an EF-hand motif from classical Ca-binding proteins such as calmodulin with a photoswitchable group that can be reversibly isomerized between a spiropyran (SP) and merocyanine (MC) state in response to different wavelengths of light.
View Article and Find Full Text PDFScience
January 2025
Redox and Metalloprotein Research Group, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
In the ancient microbial Wood-Ljungdahl pathway, carbon dioxide (CO) is fixed in a multistep process that ends with acetyl-coenzyme A (acetyl-CoA) synthesis at the bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase complex (CODH/ACS). In this work, we present structural snapshots of the CODH/ACS from the gas-converting acetogen , characterizing the molecular choreography of the overall reaction, including electron transfer to the CODH for CO reduction, methyl transfer from the corrinoid iron-sulfur protein (CoFeSP) partner to the ACS active site, and acetyl-CoA production. Unlike CODH, the multidomain ACS undergoes large conformational changes to form an internal connection to the CODH active site, accommodate the CoFeSP for methyl transfer, and protect the reaction intermediates.
View Article and Find Full Text PDFNucleic Acids Res
January 2025
Department of Medicine, UofL Health Brown Cancer Center, University of Louisville, Louisville KY, 505 S Hancock St, Louisville, KY 40202, United States.
Time-resolved small-angle X-ray experiments are reported here that capture and quantify a previously unknown rapid collapse of the unfolded oligonucleotide as an early step in the folding of hybrid 1 and hybrid 2 telomeric G-quadruplex structures. The rapid collapse, initiated by a pH jump, is characterized by an exponential decrease in the radius of gyration from 24.3 to 12.
View Article and Find Full Text PDFChem Sci
January 2025
Department of Chemical and Biological Physics, Weizmann Institute of Science Rehovot 761001 Israel
Proteins often harness extensive motions of domains and subunits to promote their function. Deciphering how these movements impact activity is key for understanding life's molecular machinery. The enzyme adenylate kinase is an intriguing example for this relationship; it ensures efficient catalysis by large-scale domain motions that lead to the enclosure of the bound substrates ATP and AMP.
View Article and Find Full Text PDFA reconfigurable holographic metasurface (HM) with multifunctional modulation of radiation and scattering for conformal applications is designed in this paper. Based on optical holography theory, a holographic conformal modulation mechanism is proposed, and the conformal surface impedance distribution of HM is derived. To illustrate this mechanism, the designed conformal reconfigurable HM is used to demonstrate a series of radiation and scattering modulation functions, with its reconfigurable property enabling dynamic beam control.
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