Impact of the G8 Score on Treatment Strategies and Outcome in Definitive Radiotherapy for the Elderly Esophageal Cancer Patients

PURPOSE/OBJECTIVE(S)

Although chemoradiotherapy (CRT) is widely used as a curative treatment for esophageal cancer, it is often difficult to perform standard CRT for the elderly in the real world. This study aimed to investigate the impact of the Geriatric 8 (G8) score on treatment strategies and outcome in definitive radiotherapy (RT) for elderly esophageal cancer patients.

MATERIALS/METHODS

We analyzed 81 esophageal cancer patients aged ≥65 years who received definitive RT between 2018 and 2021. The G8 score was acquired at the first visit to the radiation oncology department. The treatment strategy was decided by a multi-disciplinary conference, and the G8 score was not used to determine the treatment strategy. Standard treatment (standard CRT) was defined as RT with elective nodal irradiation and a total dose ≥50 Gy, and chemotherapy with two cycles of platinum (70 mg/m2) and 5FU (700 mg/m2 for 4 days) concurrently. The Kaplan-Meier method was used to generate actual survival curves. The Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 was used to assess toxicities. The Mann-Whitney U test was used to compare the two groups, and statistical significance was set at p<0.05. The Receiver Operating Characteristic (ROC) curve was used to calculate the cutoff value.

RESULTS

The Median follow-up time was 30 months (range: 8-51) for survivors. The mean G8 scores by treatment strategy were 13.9 (range: 9-17) for standard CRT group (n = 26), 12.1 (range: 7-16) for reduced CRT group (n = 30), and 9.7 (range: 4.5-14) for RT alone group (n = 25). G8 score was significantly higher for standard CRT (p = 0.017) and significantly lower for RT alone (p<0.01). The cut-off value of the G8 score for standard treatment, calculated by the ROC curve, was 12.5 points. In the non-standard treatment group, the cut-off value of the G8 score for RT alone, calculated by the ROC curve, was 10.5 points. The 2-year overall survival (OS) rates for standard CRT, reduced CRT and RT alone were 74%, 71% and 35%, respectively, and significantly lower in RT alone (p<0.001). The 2-years OS rates for G8 score >10.5 points and ≤10.5 points were 69% and 48%, respectively (p = 0.039). Grade 3 or higher acute toxicities were observed in 33 patients (41%); 14 (54%) in standard CRT, 17 (57%) in reduced CRT and 2 (8%) in RT alone. Grade 5 acute toxicity was not observed. G8 scores tended to be higher in the patients with grade 3 or higher acute toxicities, but the difference was not statistically significant (p = 0.057). Grade 3 or higher late toxicities were observed in 7 patients.

CONCLUSION

Our results suggest that there is an association between the G8 score and clinicians' treatment decisions. Although RT alone could be safely performed even in patients with low G8 scores, administration of chemotherapy strongly affected prognosis. These results suggest the importance of developing less toxic systemic therapy regimens for patients with low G8 scores.

Predictive Modeling of Radiation Pneumonitis Induced by Chemoradiotherapy for Locally Advanced Non-Small Cell Lung Cancer Using Radiomics and Clinical Features

PURPOSE/OBJECTIVE(S)

The purpose of this study is to establish a prediction model for the development of grade 2 or higher radiation pneumonitis (RP) using radiomics analysis of pretreatment CT images, PET images, and dose distribution, in addition to clinical factors, in patients with locally advanced non-small cell lung cancer (NSCLC) treated with radical chemoradiotherapy.

MATERIALS/METHODS

We retrospectively evaluated 128 cases of locally advanced NSCLC treated with radical radiotherapy at our institution from 2008 to 2021. Clinical factors included age, sex, performance status (PS), KL-6, smoking history, histological type, clinical stage, and total radiation dose. Radiomics analysis was performed by analyzing treatment planning CT images, PET images, and dose distribution, and Rad-score (Radiomics-score) was calculated for the extracted features using Lasso-Cox regression. Rad-score (Radiomics-score) was calculated by Lasso-Cox regression for the extracted features. Risk factors were selected by univariate/multivariate analysis of clinical factors and Rad-score. Three models for predicting RP were developed from the identified risk factors using Nomogram: Clinical, Rad-score, and Combined model. The model was evaluated using area under the curve (AUC) based on receiver operating characteristic (ROC) curves and concordance index (C-index). RP was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. The cumulative incidence of Grade 2 or higher RP was evaluated using the Kaplan-Meier method.

RESULTS

Of the 128 cases, grade 2 or higher RP was observed in 50 cases (39%). Regarding clinical factors, gender, smoking status, and histology were selected as significant predictors of RP. Lasso-Cox analysis of radiomics features selected 11 features from CT images, 7 features from PET images, and 16 features from dose distribution as predictors of RP, yielding a total of 34 factors. The combined model (C-index: 0.96, AUC: 0.92) showed the best discrimination performance compared to the clinical model (C-index: 0.73, AUC: 0.56) and the Rad-score model (C-index: 0.87, AUC: 0.92). Risk classification using the combined model showed that the 1-year cumulative incidence of grade 2 or higher RP was 65% in the high-risk group, significantly higher than 15% in the low-risk group (p<0.001).

CONCLUSION

The combined model with Rad-score and clinical factors can predict grade 2 or higher RP in NSCLC patients with high accuracy.

Fully First-Principles Surface Spectroscopy with Machine Learning

Our current understanding of the structure and dynamics of aqueous interfaces at the molecular level has grown substantially due to the continuous development of surface-specific spectroscopies, such as vibrational sum-frequency generation (VSFG). As in other vibrational spectroscopies, we must turn to atomistic simulations to extract all of the information encoded in the VSFG spectra. The high computational cost associated with existing methods means that they have limitations in representing systems with complex electronic structure or in achieving statistical convergence. In this work, we combine high-dimensional neural network interatomic potentials and symmetry-adapted Gaussian process regression to overcome these constraints. We show that it is possible to model VSFG signals with fully ab initio accuracy using machine learning and illustrate the versatility of our approach on the water/air interface. Our strategy allows us to identify the main sources of theoretical inaccuracy and establish a clear pathway toward the modeling of surface-sensitive spectroscopy of complex interfaces.

Data-mining unveils structure-property-activity correlation of viral infectivity enhancing self-assembling peptides

Gene therapy via retroviral vectors holds great promise for treating a variety of serious diseases. It requires the use of additives to boost infectivity. Amyloid-like peptide nanofibers (PNFs) were shown to efficiently enhance retroviral gene transfer. However, the underlying mode of action of these peptides remains largely unknown. Data-mining is an efficient method to systematically study structure-function relationship and unveil patterns in a database. This data-mining study elucidates the multi-scale structure-property-activity relationship of transduction enhancing peptides for retroviral gene transfer. In contrast to previous reports, we find that not the amyloid fibrils themselves, but rather µm-sized β-sheet rich aggregates enhance infectivity. Specifically, microscopic aggregation of β-sheet rich amyloid structures with a hydrophobic surface pattern and positive surface charge are identified as key material properties. We validate the reliability of the amphiphilic sequence pattern and the general applicability of the key properties by rationally creating new active sequences and identifying short amyloidal peptides from various pathogenic and functional origin. Data-mining-even for small datasets-enables the development of new efficient retroviral transduction enhancers and provides important insights into the diverse bioactivity of the functional material class of amyloids.

Case report: Medical treatment for limbal epithelial stem cell deficiency in patients treated for glaucoma

Limbal epithelial stem cell deficiency (LSCD) is an abnormal corneal epithelial lesion with several causes. The patient was diagnosed using fluorescein staining. Bullous keratopathy, multiple surgeries, and drug-related damage can cause LSCD in glaucoma patients. We evaluated the medical treatment course for LSCD in patients with glaucoma. We retrospectively reviewed the electronic medical records of patients diagnosed with LSCD and investigated their background, course of treatment, and classification stages of LSCD before and after treatment. The global consensus classification system (stages IA-C, IIA-B, and III) proposed by Deng et al. (Cornea 2020) was used. Seven patients (two males) and eight eyes were studied. The median age of the patients was 82 years, and the mean duration of glaucoma treatment was 8 years. The patients had open-angle glaucoma (four eyes), exfoliation glaucoma (one eye), neovascular glaucoma (one eye), normal tension glaucoma (one eye), and uveitic glaucoma (one eye). Stage classifications at diagnosis were stage IA in four eyes and stages IC, IIA, IIB, and III in one eye each. All treatments were carried out with dry eye drops, steroid eye drops, and antibiotics. The mean duration of treatment was 1.4 years. The classifications at the time of the final visit were normal corneal epithelium (three eyes), stage IA (two eyes), IIA (one eye), and III (two eyes). Three eyes (37%) improved by more than one stage and one eye deteriorated by more than one stage. LSCD is long-lasting and difficult to treat in a short period; thus, it requires careful medical attention.

Does the Sum-Frequency Generation Signal of Aromatic C-H Vibrations Reflect Molecular Orientation?

Organic molecules with aromatic groups at the aqueous interfaces play a central role in atmospheric chemistry, green chemistry, and on-water synthesis. Insights into the organization of interfacial organic molecules can be obtained using surface-specific vibrational sum-frequency generation (SFG) spectroscopy. However, the origin of the aromatic C-H stretching mode peak is unknown, prohibiting us from connecting the SFG signal to the interfacial molecular structure. Here, we explore the origin of the aromatic C-H stretching response by heterodyne-detected SFG (HD-SFG) at the liquid/vapor interface of benzene derivatives and find that, irrespective of the molecular orientation, the sign of the aromatic C-H stretching signals is negative for all the studied solvents. Together with density functional theory (DFT) calculations, we reveal that the interfacial quadrupole contribution dominates, even for the symmetry-broken benzene derivatives, although the dipole contribution is non-negligible. We propose a simple evaluation of the molecular orientation based on the aromatic C-H peak area.

Tumor-infiltrating Leukocyte Profiling Defines Three Immune Subtypes of NSCLC with Distinct Signaling Pathways and Genetic Alterations

Resistance to immune checkpoint blockade remains challenging in patients with non-small cell lung cancer (NSCLC). Tumor-infiltrating leukocyte (TIL) quantity, composition, and activation status profoundly influence responsiveness to cancer immunotherapy. This study examined the immune landscape in the NSCLC tumor microenvironment by analyzing TIL profiles of 281 fresh resected NSCLC tissues. Unsupervised clustering based on numbers and percentages of 30 TIL types classified adenocarcinoma (LUAD) and squamous cell carcinoma (LUSQ) into the cold, myeloid cell-dominant, and CD8⁺ T cell-dominant subtypes. These were significantly correlated with patient prognosis; the myeloid cell subtype had worse outcomes than the others. Integrated genomic and transcriptomic analyses, including RNA sequencing, whole-exome sequencing, T-cell receptor repertoire, and metabolomics of tumor tissue, revealed that immune reaction-related signaling pathways were inactivated, while the glycolysis and K-ras signaling pathways activated in LUAD and LUSQ myeloid cell subtypes. Cases with ALK and ROS1 fusion genes were enriched in the LUAD myeloid subtype, and the frequency of TERT copy-number variations was higher in LUSQ myeloid subtype than in the others. These classifications of NSCLC based on TIL status may be useful for developing personalized immune therapies for NSCLC.

Significance

The precise TIL profiling classified NSCLC into novel three immune subtypes that correlates with patient outcome, identifying subtype-specific molecular pathways and genomic alterations that should play important roles in constructing subtype-specific immune tumor microenvironments. These classifications of NSCLC based on TIL status are useful for developing personalized immune therapies for NSCLC.

Fibril formation and ordering of disordered FUS LC driven by hydrophobic interactions

Biomolecular condensates, protein-rich and dynamic membrane-less organelles, play critical roles in a range of subcellular processes, including membrane trafficking and transcriptional regulation. However, aberrant phase transitions of intrinsically disordered proteins in biomolecular condensates can lead to the formation of irreversible fibrils and aggregates that are linked to neurodegenerative diseases. Despite the implications, the interactions underlying such transitions remain obscure. Here we investigate the role of hydrophobic interactions by studying the low-complexity domain of the disordered 'fused in sarcoma' (FUS) protein at the air/water interface. Using surface-specific microscopic and spectroscopic techniques, we find that a hydrophobic interface drives fibril formation and molecular ordering of FUS, resulting in solid-like film formation. This phase transition occurs at 600-fold lower FUS concentration than required for the canonical FUS low-complexity liquid droplet formation in bulk. These observations highlight the importance of hydrophobic effects for protein phase separation and suggest that interfacial properties drive distinct protein phase-separated structures.

True Origin of Amide I Shifts Observed in Protein Spectra Obtained with Sum Frequency Generation Spectroscopy

Accurate determination of protein structure at interfaces is critical for understanding protein interactions, which is directly relevant to a molecular-level understanding of interfacial proteins in biology and medicine. Vibrational sum frequency generation (VSFG) spectroscopy is often used for probing the protein amide I mode, which reports protein structures at interfaces. Observed peak shifts are attributed to conformational changes and often form the foundation of hypotheses explaining protein working mechanisms. Here, we investigate structurally diverse proteins using conventional and heterodyne-detected VSFG (HD-VSFG) spectroscopy as a function of solution pH. We reveal that blue-shifts of the amide I peak observed in conventional VSFG spectra upon lowering the pH are governed by the drastic change of the nonresonant contribution. Our results highlight that connecting changes in conventional VSFG spectra to conformational changes of interfacial proteins can be arbitrary, and that HD-VSFG measurements are required to draw unambiguous conclusions about structural changes in biomolecules.

Ions Speciation at the Water-Air Interface

In typical aqueous systems, including naturally occurring sweet and salt water and tap water, multiple ion species are co-solvated. At the water-air interface, these ions are known to affect the chemical reactivity, aerosol formation, climate, and water odor. Yet, the composition of ions at the water interface has remained enigmatic. Here, using surface-specific heterodyne-detected sum-frequency generation spectroscopy, we quantify the relative surface activity of two co-solvated ions in solution. We find that more hydrophobic ions are speciated to the interface due to the hydrophilic ions. Quantitative analysis shows that the interfacial hydrophobic ion population increases with decreasing interfacial hydrophilic ion population at the interface. Simulations show that the solvation energy difference between the ions and the intrinsic surface propensity of ions determine the extent of an ion's speciation by other ions. This mechanism provides a unified view of the speciation of monatomic and polyatomic ions at electrolyte solution interfaces.

Designed Production of Atomic-Scale Nanowindows in Single-Walled Carbon Nanotubes

The controlled production of nanowindows in graphene layers is desirable for the development of ultrathin membranes. Herein, we propose a single-atom catalytic oxidation method for introducing nanowindows into the graphene layers of single-walled carbon nanotubes (SWCNTs). Using liquid-phase adsorption, copper(II) 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine (CuPc) was adsorbed on SWCNT bundles at a surface coverage of 0.9. Subsequently, narrow nanowindows with a number density of 0.13 nm^-2 were produced by oxidation above 550 K, which is higher than the decomposition temperature of bulk CuPc. In particular, oxidation of the CuPc-adsorbed SWCNTs at 623 K increased the surface area from 280 to 1690 m² g^-1 owing to the efficient production of nanowindows. The nanowindow size was estimated to be similar to the molecular size of N₂ based on the pronounced low-pressure adsorption hysteresis in the N₂ adsorption isotherm. In addition, the enthalpy change for the nanowindow-formation equilibrium decreased by 4 kJ mol^-1 when CuPc was present, further evidencing the catalytic effect of the Cu atoms supplied by the adsorbed CuPc molecules.

Is Unified Understanding of Vibrational Coupling of Water Possible? Hyper-Raman Measurement and Machine Learning Spectra

The impact of the vibrational coupling of the OH stretch mode on the spectra differs significantly between IR and Raman spectra of water. Unified understanding of the vibrational couplings is not yet achieved. By using a different class of vibrational spectroscopy, hyper-Raman (HR) spectroscopy, together with machine-learning-assisted HR spectra calculation, we examine the impact of the vibrational couplings of water through the comparison of isotopically diluted H₂O and pure H₂O. We found that the isotopic dilution reduces the HR bandwidths, but the impact of the vibrational coupling is smaller than in the IR and parallel-polarized Raman. Machine learning HR spectra indicate that the intermolecular coupling plays a major role in broadening the bandwidth, while the intramolecular coupling is negligibly small, which is consistent with the IR and Raman spectra. Our result clearly demonstrates a limited impact of the intramolecular vibration, independent of the selection rules of vibrational spectroscopies.

Direct Probe of Electrochemical Pseudocapacitive pH Jump at a Graphene Electrode

Molecular-level insight into interfacial water at a buried electrode interface is essential in electrochemistry, but spectroscopic probing of the interface remains challenging. Here, using surface-specific heterodyne-detected sum-frequency generation (HD-SFG) spectroscopy, we directly access the interfacial water in contact with the graphene electrode supported on calcium fluoride (CaF₂ ). We find phase transition-like variations of the HD-SFG spectra vs. applied potentials, which arises not from the charging/discharging of graphene but from the charging/discharging of the CaF₂ substrate through the pseudocapacitive process. The potential-dependent spectra are nearly identical to the pH-dependent spectra, evidencing that the pseudocapacitive behavior is associated with a substantial local pH change induced by water dissociation between the CaF₂ and graphene. Our work evidences the local molecular-level effects of pseudocapacitive charging at an electrode/aqueous electrolyte interface.

On the Fresnel factor correction of sum-frequency generation spectra of interfacial water

Insights into the microscopic structure of aqueous interfaces are essential for understanding the chemical and physical processes on the water surface, including chemical synthesis, atmospheric chemistry, and events in biomolecular systems. These aqueous interfaces have been probed by heterodyne-detected sum-frequency generation (HD-SFG) spectroscopy. To obtain the molecular response from the measured HD-SFG spectra, one needs to correct the measured ssp spectra for local electromagnetic field effects at the interface due to a spatially varying dielectric function. This so-called Fresnel factor correction can change the inferred response substantially, and different ways of performing this correction lead to different conclusions about the interfacial water response. Here, we compare the simulated and experimental spectra at the air/water interface. We use three previously developed models to compare the experiment with theory: an advanced approach taking into account the detailed inhomogeneous interfacial dielectric profile and the Lorentz and slab models to approximate the interfacial dielectric function. Using the advanced model, we obtain an excellent quantitative agreement between theory and experiment, in both spectral shape and amplitude. Remarkably, we find that for the Fresnel factor correction of the ssp spectra, the Lorentz model for the interfacial dielectric function is equally accurate in the hydrogen (H)-bonded region of the response, while the slab model underestimates this response significantly. The Lorentz model, thus, provides a straightforward method to obtain the molecular response from the measured spectra of aqueous interfaces in the H-bonded region.

Efficacy and safety of a fixed combination of 1% brinzolamide and 0.1% brimonidine as treatment for glaucoma: a retrospective study focusing on the number of ingredients

OBJECTIVE

To evaluate the intraocular pressure (IOP)-lowering effect based on the number of ingredients and survival rate due to adverse reactions of brinzolamide (1%)/brimonidine (0.1%) fixed combination (BBFC).

METHODS AND ANALYSIS

Among 424 patients newly administered BBFC from June 2020 to May 2021, 406 were retrospectively evaluated for adverse reactions and 299 were evaluated for the IOP-lowering effect of BBFC. Among those evaluated for IOP, group A (n=86) included patients whose treatment was changed to BBFC from other two ingredients, Group B (n=90) included patients who added one ingredient by switching to BBFC, and group C (n=123) included patients who added BBFC in addition to other drugs.

RESULTS

The mean IOP (mm Hg) at BBFC initiation and at 3, 6 and 12 months after BBFC initiation was 14.1, 14.0, 14.3 and 13.8 in group A, 15.9, 14.4, 13.8 and 14.5 in group B and 17.2, 14.0, 14.1 and 14.9 in group C, respectively. Group A showed no significant difference in mean IOP from baseline to any time point after BBFC initiation, whereas groups B and C showed significant IOP reductions at all time points. Seventy-three (18%) patients discontinued treatment due to adverse reactions. The survival rate was 72% at 12 months after the start of BBFC when discontinuation due to adverse reactions was defined as failure.

CONCLUSION

Using BBFC, sustained IOP or decreasing IOP were observed depending on the number of ingredients. Drop-outs due to the adverse reactions should also be given attention.

Improvement in the mobility of a patient with fibroblast growth factor 23-related hypophosphatemic osteomalacia and decompensated liver cirrhosis in response to burosumab: a case report

Acquired fibroblast growth factor (FGF) 23-related hypophosphatemic osteomalacia is characterized clinically by muscle weakness, bone pain, and fractures. Its biochemical features include hypophosphatemia, caused by renal phosphate wasting, and inappropriately normal or low 1,25-dihydroxy-vitamin D levels. Recently, burosumab, a fully human monoclonal antibody targeting FGF23, was approved for the treatment of FGF23-related hypophosphatemic rickets and osteomalacia. We report the case of a 75-year-old Japanese woman with decompensated liver cirrhosis and hepatic encephalopathy, caused by primary biliary cholangitis, who complained of back pain and limited mobility resulting from multiple vertebral fractures. She was not receiving iron infusion therapy and denied alcohol consumption. The patient exhibited hypophosphatemia with a low tubular maximum reabsorption of phosphate per unit glomerular filtration rate (TmP/GFR) and a high circulating concentration of FGF23. Conventional therapy with alfacalcidol and oral phosphate slightly improved her serum phosphate concentration and back pain, but she experienced a hip fracture, causing her to become wheelchair-dependent. Burosumab was initiated 8 weeks after the hip fracture, which increased her serum phosphate concentration and TmP/GFR. Her mobility gradually improved, such that she could walk without a cane after 16 weeks of treatment. Her lumbar bone mineral density increased after 48 weeks. Hepatic encephalopathy developed once before the initiation of treatment and twice after the initiation of the therapy, but her liver function was preserved. This is the first study to report the efficacy and safety of burosumab treatment for FGF23-related hypophosphatemic osteomalacia with decompensated liver cirrhosis.

TB-related technical enquiries received in Japan, 2017-2019

SETTING

Japan, an intermediate TB burden country.

OBJECTIVE

To review TB-related technical enquiries received at the Research Institute of Tuberculosis, Japan, from January 2017 to December 2019.

DESIGN

This was a cohort study.

RESULTS

A total of 2,197 enquiries were analysed. On average, 61.0 enquiries/month (range: 42-81) were received. The enquiry rates were highest for the Yamanashi (4.65/100,000 population) and Ishikawa (4.55) Prefectures, and lowest in the Yamagata (0.46) and Tochigi (0.56) Prefectures. The main organisations the enquirers belonged to were local governments (n = 1,585, 72.1%) and healthcare facilities (n = 307, 14.0%). The enquirers were medical doctors (n = 391, 17.8%), nurses (n = 1,207, 54.9%), other healthcare professionals (n = 57, 2.6%), the general public (n = 168, 7.6%) and others/unknown (n = 374, 17.0%). The most frequent enquiries were about TB diagnosis and treatment (n = 501, 22.8%), including laboratory diagnosis (n = 88, 4.0%), TB treatment in general (n = 93, 4.2%) and management of comorbidities (n = 86, 3.9%), followed by contact investigations (n = 385, 17.5%) and TB in foreigners (n = 344, 15.7%).

CONCLUSION

As the most frequent enquiries were about diagnosis and treatment of TB, the health ministry of Japan should maintain a few specialised TB institutions with TB physicians to provide technical assistance.

Targeted deep sequencing analyses of long QT syndrome in a Japanese population

Long QT syndrome (LQTS) is one of the most common inherited arrhythmias and multiple genes have been reported as causative. Presently, genetic diagnosis for LQTS patients is becoming widespread and contributing to implementation of therapies. However, causative genetic mutations cannot be detected in about 20% of patients. To elucidate additional genetic mutations in LQTS, we performed deep-sequencing of previously reported 15 causative and 85 candidate genes for this disorder in 556 Japanese LQTS patients. We performed in-silico filtering of the sequencing data and found 48 novel variants in 33 genes of 53 cases. These variants were predicted to be damaging to coding proteins or to alter the binding affinity of several transcription factors. Notably, we found that most of the LQTS-related variants in the RYR2 gene were in the large cytoplasmic domain of the N-terminus side. They might be useful for screening of LQTS patients who had no known genetic factors. In addition, when the mechanisms of these variants in the development of LQTS are revealed, it will be useful for early diagnosis, risk stratification, and selection of treatment.

Theoretical Sum Frequency Generation Spectra of Protein Amide with Surface-Specific Velocity-Velocity Correlation Functions

Vibrational sum frequency generation (vSFG) spectroscopy is widely used to probe the protein structure at interfaces. Because protein vSFG spectra are complex, they can only provide detailed structural information if combined with computer simulations of protein molecular dynamics and spectra calculations. We show how vSFG spectra can be accurately modeled using a surface-specific velocity-velocity scheme based on ab initio normal modes. Our calculated vSFG spectra show excellent agreement with the experimental sum frequency spectrum of LTα14 peptide and provide insight into the origin of the characteristic α-helical amide I peak. Analysis indicates that the peak shape can be explained largely by two effects: (1) the uncoupled response of amide groups located on opposite sides of the α-helix will have different orientations with respect to the interface and therefore different local environments affecting the local mode vibrations and (2) vibrational splitting from nearest neighbor coupling evaluated as inter-residue vibrational correlation. The conclusion is consistent with frequency mapping techniques with an empirically based ensemble of peptide structures, thus showing how time correlation approaches and frequency mapping techniques can give independent yet complementary molecular descriptions of protein vSFG. These models reveal the sensitive relationship between protein structure and their amide I response, allowing exploitation of the complicated molecular vibrations and their interference to derive the structures of proteins under native conditions at interfaces.