Breast Implant Imaging Surveillance Practice: Survey of Breast Imaging Radiologists in the Society of Breast Imaging.

OBJECTIVE: The objectives of this Society of Breast Imaging (SBI)-member survey study were to assess the current imaging patterns for evaluation of symptomatic and asymptomatic breast implant integrity, including modalities used and imaging intervals. METHODS: A 12-question survey assessing the frequency of imaging modalities used to evaluate implant integrity, approximate number of breast implant integrity studies requested per month, intervals of integrity studies, and referring provider and radiology practice characteristics was distributed to members of the SBI. RESULTS: The survey response rate was 7.6% (143/1890). Of responding radiologists, 54.2% (77/142) were in private, 29.6% (42/142) in academic, and 16.2% (23/142) in hybrid practice. Among respondents, the most common initial examination for evaluating implant integrity was MRI without contrast at 53.1% (76/143), followed by handheld US at 46.9% (67/143). Of respondents using US, 67.4% (91/135) also evaluated the breast tissue for abnormalities. Among respondents, 34.1% (46/135) reported being very confident or confident in US for diagnosing implant rupture. There was a range of reported intervals for performing implant integrity studies: 39.1% (43/110) every 2-3 years, 26.4% (29/110) every 4-5 years, 15.5% (17/110) every 6-10 years, and 19.1% (21/110) every 10 years. CONCLUSION: For assessment of implant integrity, the majority of respondents (53.2%, 76/143) reported MRI as initial imaging test. US is less costly, but the minority of respondents (34.1%, 46/135) had confidence in US performance. Also, the minority of respondents (39.1%, 43/110) performed implant integrity evaluations every 2-3 years per the FDA recommendations for asymptomatic surveillance.

Unraveling Complex Local Protein Environments with 4-Cyano-l-phenylalanine.

We present a multifaceted approach to effectively probe complex local protein environments utilizing the vibrational reporter unnatural amino acid (UAA) 4-cyano-l-phenylalanine (pCNPhe) in the model system superfolder green fluorescent protein (sfGFP). This approach combines temperature-dependent infrared (IR) spectroscopy, X-ray crystallography, and molecular dynamics (MD) simulations to provide a molecular interpretation of the local environment of the nitrile group in the protein. Specifically, a two-step enantioselective synthesis was developed that provided an 87% overall yield of pCNPhe in high purity without the need for chromatography. It was then genetically incorporated individually at three unique sites (74, 133, and 149) in sfGFP to probe these local protein environments. The incorporation of the UAA site-specifically in sfGFP utilized an engineered, orthogonal tRNA synthetase in E. coli using the Amber codon suppression protocol, and the resulting UAA-containing sfGFP constructs were then explored with this approach. This methodology was effectively utilized to further probe the local environments of two surface sites (sites 133 and 149) that we previously explored with room temperature IR spectroscopy and X-ray crystallography and a new interior site (site 74) featuring a complex local environment around the nitrile group of pCNPhe. Site 133 was found to be solvent-exposed, while site 149 was partially buried. Site 74 was found to consist of three distinct local environments around the nitrile group including nonspecific van der Waals interactions, hydrogen-bonding to a structural water, and hydrogen-bonding to a histidine side chain.

Structural and spectrophotometric investigation of two unnatural amino-acid altered chromophores in the superfolder green fluorescent protein.

The spectrophotometric properties of the green fluorescent protein (GFP) result from the post-translationally cyclized chromophore composed of three amino acids including a tyrosine at the center of the ß-barrel protein. Altering the amino acids in the chromophore or the nearby region has resulted in numerous GFP variants with differing photophysical properties. To further examine the effect of small atomic changes in the chromophore on the structure and photophysical properties of GFP, the hydroxyl group of the chromophore tyrosine was replaced with a nitro or a cyano group. The structures and spectrophotometric properties of these superfolder GFP (sfGFP) variants with the unnatural amino acids (UAAs) 4-nitro-L-phenylalanine or 4-cyano-L-phenylalanine were explored. Notably, the characteristic 487 nm absorbance band of wild-type (wt) sfGFP is absent in both unnatural amino-acid-containing protein constructs (Tyr66pNO2Phe-sfGFP and Tyr66pCNPhe-sfGFP). Consequently, neither Tyr66pNO2Phe-sfGFP nor Tyr66pCNPhe-sfGFP exhibited the characteristic emission of wt sfGFP centered at 511 nm when excited at 487 nm. Tyr66pNO2Phe-sfGFP appeared orange due to an absorbance band centered at 406 nm that was not present in wt sfGFP, while Tyr66pCNPhe-sfGFP appeared colorless with an absorbance band centered at 365 nm. Mass spectrometry and X-ray crystallography confirmed the presence of a fully formed chromophore and no significant structural changes in either of these UAA-containing protein constructs, signaling that the change in the observed photophysical properties of the proteins is the result of the presence of the UAA in the chromophore.