J-1700 Circular Dichroism Spectrophotometer

System Description

The J-1700 was specifically designed for more demanding near-infrared CD applications. In addition to the enhanced far-UV capabilities, researchers probing the chiral activity of molecules in the NIR spectral region can now obtain data at wavelengths up to 2500 nm. The InGaAs detector has a wavelength range from 900-2500 nm, while the PMT ranges from 163-960 nm. The automatic detector interchange allows researchers to obtain both far-UV and NIR measurements without having to manually switch detectors. The addition of a grating monochromator to the double-prism monochromator setup provides low stray light and high light intensity, generating CD signals with high S/N performance throughout a large spectral range.

NIR-CD applications vary from conformational and chirality studies of metal coordination complexes to tuning chiral properties of nanomaterials. Additionally, Magnetic Circular Dichroism (MCD) can be used in conjunction with NIR-CD to probe a chromophore’s electronic structure as well as to induce chirality in compounds.

Stopped-flow measurements involve the rapid mixing of two or more solutions to trigger a chemical reaction, the kinetics of which can be followed by CD, absorbance and fluorescence. All probe methods can be measured on the same instrument when the stopped-flow system is paired with a J-1700 Spectrometer as well as a J-1500.

Advanced Features

• High optical throughput
• Double prism monochromator providing low stray light
• Wide dynamic range PMT detector
• Highly efficient nitrogen purge system
• Digital signal processing
• Simultaneous Multi-Probe: CD, LD, HT, DC, absorbance, fluorescence
• Triple detector system, automatically selected by the software, able to assure the maximum sensitivity in the whole spectral range, from 163nm up to 2500nm
• Dual monochromator system (double prism system for UV/Vis and grating for NIR range) with automatic switching
• Dual lamp system (Halogen and Xenon) with automatic switching
• Continuous Scan, Step Scan, and Auto-Scan available on the same instrument. Working in Continuous Scan, unlike a system working only in Step Scan, allows fast analysis in case the operating conditions or method are not optimized

Unique Benefits and Accessories

• Compact benchtop design
• Range of precise temperature control accessories
• High-throughput automated CD
• Automated titration and stopped-flow
• Spectra Manager™ software for control and extensive data analysis
• Flexible design allows field upgrades for different measurement capabilities as applications and budgets evolve

Enhanced vacuum-UV measurement

The innovative optical system of the J-1500 permits the measurement of a CD spectrum in the vacuum-UV region down to 163 nm. The enhanced light throughput and new digital lock-in technology now allow for a small signal in a very noisy environment to be detected. Additionally, the optimisation of the nitrogen purge efficiency helps to reduce the amount of oxygen in the optical bench so that it does not bury the sample signal.

These features ensure that CD spectra can be obtained from strongly absorbing and high signal-to-noise (S/N) samples across the spectrum and into the vacuum-UV region. The quality of spectral data obtained, including data obtained at shorter wavelengths, substantially improves the accuracy of protein secondary structure analysis.

High Sensitivity and Wide Dynamic Range of PMT Detector

The PMT detectors used in the JASCO system are specially selected for the highest sensitivity and lowest birefringence. The wide dynamic range of the PMT detector ensures that large variations in signal intensity can still be detected, even for highly absorbing samples. The result is superior linearity between concentration and absorbance compared to other types of detectors including solid-state APD and CCD detectors.

The gain on a PMT detector is much larger (107) than most detectors, and therefore, the signal amplification is larger. Under conditions with adequate light intensity, this typically leads to a larger amount of noise and therefore a lower S/N ratio. However, under conditions where there is a small amount of light hitting the detector (i.e. far-UV region), the gain of the PMT allows for good signal amplification at very low noise, increasing the S/N ratio.

Exceptional stray-light rejection

The double polarizing prism monochromators of the J-1000 series result in stray light lower than 0.0003%, enabling the instruments to obtain high-quality CD data even under conditions with high absorbances.

Simultaneous Multi-Probe Measurements

The latest quad-channel lock-in amplifier provides simultaneous acquisition of up to four data channels, including CD, HT, DC, absorbance, linear dichroism (LD), fluorescence, fluorescence-detected CD (FDCD), fluorescence-detected LD (FDLD) and fluorescence anisotropy.

Additionally, the lock-in amplifier obtains a signal at a specific resonance frequency while filtering out noise signals at other frequencies, helping to provide spectra with excellent signal-to-noise ratios.

Rapid Scanning

High sensitivity combined with a 10,000 nm-per-minute maximum scan speed allows the J-1500 to measure samples quickly, increasing productivity in your lab. An additional benefit is the minimal time exposure of biological samples to the high-energy UV light, minimizing the risk of sample degradation. A mechanical shutter can also be programmed to open and close only during actual measurement to further avoid UV exposure.

Highest S/N Performance

The high S/N (signal-to-noise) performance of the J-1000 series is achieved by a high-throughput optical system and low-noise signal processing. RMS Noise < 0.004 mdeg (185 nm) for the J-1500 and J-1700, < 0.03 mdeg (200 nm) for J-1100.